diff --git a/programs/lz4cli.c b/programs/lz4cli.c
index d7d4f81..523b8a8 100644
--- a/programs/lz4cli.c
+++ b/programs/lz4cli.c
@@ -93,11 +93,11 @@ static unsigned displayLevel = 2;   /* 0 : no display ; 1: errors only ; 2 : dow
 ***************************************/
 #define DEFAULT_COMPRESSOR   LZ4IO_compressFilename
 #define DEFAULT_DECOMPRESSOR LZ4IO_decompressFilename
-int LZ4IO_compressFilename_Legacy(LZ4IO_prefs_t* const prefs, const char* input_filename, const char* output_filename, int compressionlevel);   /* hidden function */
-int LZ4IO_compressMultipleFilenames_Legacy(LZ4IO_prefs_t* const prefs,
+int LZ4IO_compressFilename_Legacy(const char* input_filename, const char* output_filename, int compressionlevel, const LZ4IO_prefs_t* prefs);   /* hidden function */
+int LZ4IO_compressMultipleFilenames_Legacy(
                             const char** inFileNamesTable, int ifntSize,
                             const char* suffix,
-                            int compressionLevel);
+                            int compressionLevel, const LZ4IO_prefs_t* prefs);
 
 /*-***************************
 *  Functions
@@ -747,10 +747,11 @@ int main(int argc, const char** argv)
     if (ifnIdx == 0) multiple_inputs = 0;
     if (mode == om_decompress) {
         if (multiple_inputs) {
+            const char* const dec_extension = !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION;
             assert(ifnIdx <= INT_MAX);
-            operationResult = LZ4IO_decompressMultipleFilenames(prefs, inFileNames, (int)ifnIdx, !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION);
+            operationResult = LZ4IO_decompressMultipleFilenames(inFileNames, (int)ifnIdx, dec_extension, prefs);
         } else {
-            operationResult = DEFAULT_DECOMPRESSOR(prefs, input_filename, output_filename);
+            operationResult = DEFAULT_DECOMPRESSOR(input_filename, output_filename, prefs);
         }
     } else if (mode == om_list){
         operationResult = LZ4IO_displayCompressedFilesInfo(inFileNames, ifnIdx);
@@ -758,16 +759,18 @@ int main(int argc, const char** argv)
         if (legacy_format) {
             DISPLAYLEVEL(3, "! Generating LZ4 Legacy format (deprecated) ! \n");
             if(multiple_inputs){
-                LZ4IO_compressMultipleFilenames_Legacy(prefs, inFileNames, (int)ifnIdx, !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION, cLevel);
+                const char* const leg_extension = !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION;
+                LZ4IO_compressMultipleFilenames_Legacy(inFileNames, (int)ifnIdx, leg_extension, cLevel, prefs);
             } else {
-                LZ4IO_compressFilename_Legacy(prefs, input_filename, output_filename, cLevel);
+                LZ4IO_compressFilename_Legacy(input_filename, output_filename, cLevel, prefs);
             }
         } else {
             if (multiple_inputs) {
+                const char* const comp_extension = !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION;
                 assert(ifnIdx <= INT_MAX);
-                operationResult = LZ4IO_compressMultipleFilenames(prefs, inFileNames, (int)ifnIdx, !strcmp(output_filename,stdoutmark) ? stdoutmark : LZ4_EXTENSION, cLevel);
+                operationResult = LZ4IO_compressMultipleFilenames(inFileNames, (int)ifnIdx, comp_extension, cLevel, prefs);
             } else {
-                operationResult = DEFAULT_COMPRESSOR(prefs, input_filename, output_filename, cLevel);
+                operationResult = DEFAULT_COMPRESSOR(input_filename, output_filename, cLevel, prefs);
     }   }   }
 
 _cleanup:
diff --git a/programs/lz4io.c b/programs/lz4io.c
index 302d747..4c4678c 100644
--- a/programs/lz4io.c
+++ b/programs/lz4io.c
@@ -178,7 +178,7 @@ LZ4IO_prefs_t* LZ4IO_defaultPreferences(void)
     return ret;
 }
 
-void LZ4IO_freePreferences(LZ4IO_prefs_t* const prefs)
+void LZ4IO_freePreferences(LZ4IO_prefs_t* prefs)
 {
     free(prefs);
 }
@@ -396,9 +396,8 @@ static int LZ4IO_LZ4_compress(const char* src, char* dst, int srcSize, int dstSi
 /* LZ4IO_compressFilename_Legacy :
  * This function is intentionally "hidden" (not published in .h)
  * It generates compressed streams using the old 'legacy' format */
-int LZ4IO_compressFilename_Legacy(LZ4IO_prefs_t* const prefs,
-                                  const char* input_filename, const char* output_filename,
-                                  int compressionlevel)
+int LZ4IO_compressFilename_Legacy(const char* input_filename, const char* output_filename,
+                                  int compressionlevel, const LZ4IO_prefs_t* prefs)
 {
     typedef int (*compress_f)(const char* src, char* dst, int srcSize, int dstSize, int cLevel);
     compress_f const compressionFunction = (compressionlevel < 3) ? LZ4IO_LZ4_compress : LZ4_compress_HC;
@@ -483,10 +482,10 @@ int LZ4IO_compressFilename_Legacy(LZ4IO_prefs_t* const prefs,
 /* LZ4IO_compressMultipleFilenames_Legacy :
  * This function is intentionally "hidden" (not published in .h)
  * It generates multiple compressed streams using the old 'legacy' format */
-int LZ4IO_compressMultipleFilenames_Legacy(LZ4IO_prefs_t* const prefs,
+int LZ4IO_compressMultipleFilenames_Legacy(
                             const char** inFileNamesTable, int ifntSize,
                             const char* suffix,
-                            int compressionLevel)
+                            int compressionLevel, const LZ4IO_prefs_t* prefs)
 {
     int i;
     int missed_files = 0;
@@ -500,9 +499,9 @@ int LZ4IO_compressMultipleFilenames_Legacy(LZ4IO_prefs_t* const prefs,
     for (i=0; i<ifntSize; i++) {
         size_t const ifnSize = strlen(inFileNamesTable[i]);
         if (!strcmp(suffix, stdoutmark)) {
-            missed_files += LZ4IO_compressFilename_Legacy(prefs,
+            missed_files += LZ4IO_compressFilename_Legacy(
                                     inFileNamesTable[i], stdoutmark,
-                                    compressionLevel);
+                                    compressionLevel, prefs);
             continue;
         }
 
@@ -516,9 +515,9 @@ int LZ4IO_compressMultipleFilenames_Legacy(LZ4IO_prefs_t* const prefs,
         strcpy(dstFileName, inFileNamesTable[i]);
         strcat(dstFileName, suffix);
 
-        missed_files += LZ4IO_compressFilename_Legacy(prefs,
+        missed_files += LZ4IO_compressFilename_Legacy(
                                 inFileNamesTable[i], dstFileName,
-                                compressionLevel);
+                                compressionLevel, prefs);
     }
 
     /* Close & Free */
@@ -610,7 +609,7 @@ static LZ4F_CDict* LZ4IO_createCDict(const LZ4IO_prefs_t* const prefs)
     return cdict;
 }
 
-static cRess_t LZ4IO_createCResources(LZ4IO_prefs_t* const prefs)
+static cRess_t LZ4IO_createCResources(const LZ4IO_prefs_t* const prefs)
 {
     const size_t blockSize = prefs->blockSize;
     cRess_t ress;
@@ -644,14 +643,13 @@ static void LZ4IO_freeCResources(cRess_t ress)
 
 /*
  * LZ4IO_compressFilename_extRess()
- * io_prefs is mutable, as it may update sparseFileSupport
  * result : 0 : compression completed correctly
  *          1 : missing or pb opening srcFileName
  */
 static int
-LZ4IO_compressFilename_extRess(LZ4IO_prefs_t* const io_prefs, cRess_t ress,
+LZ4IO_compressFilename_extRess(cRess_t ress,
                                const char* srcFileName, const char* dstFileName,
-                               int compressionLevel)
+                               int compressionLevel, const LZ4IO_prefs_t* const io_prefs)
 {
     unsigned long long filesize = 0;
     unsigned long long compressedfilesize = 0;
@@ -773,13 +771,13 @@ LZ4IO_compressFilename_extRess(LZ4IO_prefs_t* const io_prefs, cRess_t ress,
 }
 
 
-int LZ4IO_compressFilename(LZ4IO_prefs_t* const prefs, const char* srcFileName, const char* dstFileName, int compressionLevel)
+int LZ4IO_compressFilename(const char* srcFileName, const char* dstFileName, int compressionLevel, const LZ4IO_prefs_t* prefs)
 {
     UTIL_time_t const timeStart = UTIL_getTime();
     clock_t const cpuStart = clock();
     cRess_t const ress = LZ4IO_createCResources(prefs);
 
-    int const result = LZ4IO_compressFilename_extRess(prefs, ress, srcFileName, dstFileName, compressionLevel);
+    int const result = LZ4IO_compressFilename_extRess(ress, srcFileName, dstFileName, compressionLevel, prefs);
 
     /* Free resources */
     LZ4IO_freeCResources(ress);
@@ -797,10 +795,11 @@ int LZ4IO_compressFilename(LZ4IO_prefs_t* const prefs, const char* srcFileName,
 }
 
 
-int LZ4IO_compressMultipleFilenames(LZ4IO_prefs_t* const prefs,
+int LZ4IO_compressMultipleFilenames(
                               const char** inFileNamesTable, int ifntSize,
                               const char* suffix,
-                              int compressionLevel)
+                              int compressionLevel,
+                              const LZ4IO_prefs_t* prefs)
 {
     int i;
     int missed_files = 0;
@@ -816,9 +815,9 @@ int LZ4IO_compressMultipleFilenames(LZ4IO_prefs_t* const prefs,
     for (i=0; i<ifntSize; i++) {
         size_t const ifnSize = strlen(inFileNamesTable[i]);
         if (!strcmp(suffix, stdoutmark)) {
-            missed_files += LZ4IO_compressFilename_extRess(prefs, ress,
+            missed_files += LZ4IO_compressFilename_extRess(ress,
                                     inFileNamesTable[i], stdoutmark,
-                                    compressionLevel);
+                                    compressionLevel, prefs);
             continue;
         }
         if (ofnSize <= ifnSize+suffixSize+1) {
@@ -832,9 +831,9 @@ int LZ4IO_compressMultipleFilenames(LZ4IO_prefs_t* const prefs,
         strcpy(dstFileName, inFileNamesTable[i]);
         strcat(dstFileName, suffix);
 
-        missed_files += LZ4IO_compressFilename_extRess(prefs, ress,
+        missed_files += LZ4IO_compressFilename_extRess(ress,
                                 inFileNamesTable[i], dstFileName,
-                                compressionLevel);
+                                compressionLevel, prefs);
     }
 
     /* Close & Free */
@@ -1260,9 +1259,9 @@ LZ4IO_decompressSrcFile(dRess_t ress,
 
 
 static int
-LZ4IO_decompressDstFile(LZ4IO_prefs_t* const prefs,
-                        dRess_t ress,
-                        const char* input_filename, const char* output_filename)
+LZ4IO_decompressDstFile(dRess_t ress,
+                        const char* input_filename, const char* output_filename,
+                        const LZ4IO_prefs_t* const prefs)
 {
     stat_t statbuf;
     int stat_result = 0;
@@ -1290,12 +1289,12 @@ LZ4IO_decompressDstFile(LZ4IO_prefs_t* const prefs,
 }
 
 
-int LZ4IO_decompressFilename(LZ4IO_prefs_t* const prefs, const char* input_filename, const char* output_filename)
+int LZ4IO_decompressFilename(const char* input_filename, const char* output_filename, const LZ4IO_prefs_t* prefs)
 {
     dRess_t const ress = LZ4IO_createDResources(prefs);
     clock_t const start = clock();
 
-    int const missingFiles = LZ4IO_decompressDstFile(prefs, ress, input_filename, output_filename);
+    int const missingFiles = LZ4IO_decompressDstFile(ress, input_filename, output_filename, prefs);
 
     clock_t const end = clock();
     double const seconds = (double)(end - start) / CLOCKS_PER_SEC;
@@ -1306,9 +1305,10 @@ int LZ4IO_decompressFilename(LZ4IO_prefs_t* const prefs, const char* input_filen
 }
 
 
-int LZ4IO_decompressMultipleFilenames(LZ4IO_prefs_t* const prefs,
-                                const char** inFileNamesTable, int ifntSize,
-                                const char* suffix)
+int LZ4IO_decompressMultipleFilenames(
+                            const char** inFileNamesTable, int ifntSize,
+                            const char* suffix,
+                            const LZ4IO_prefs_t* prefs)
 {
     int i;
     int skippedFiles = 0;
@@ -1341,7 +1341,7 @@ int LZ4IO_decompressMultipleFilenames(LZ4IO_prefs_t* const prefs,
         }
         memcpy(outFileName, inFileNamesTable[i], ifnSize - suffixSize);
         outFileName[ifnSize-suffixSize] = '\0';
-        missingFiles += LZ4IO_decompressDstFile(prefs, ress, inFileNamesTable[i], outFileName);
+        missingFiles += LZ4IO_decompressDstFile(ress, inFileNamesTable[i], outFileName, prefs);
     }
 
     LZ4IO_freeDResources(ress);
diff --git a/programs/lz4io.h b/programs/lz4io.h
index 4763180..d6d7eee 100644
--- a/programs/lz4io.h
+++ b/programs/lz4io.h
@@ -55,7 +55,7 @@
 typedef struct LZ4IO_prefs_s LZ4IO_prefs_t;
 
 LZ4IO_prefs_t* LZ4IO_defaultPreferences(void);
-void LZ4IO_freePreferences(LZ4IO_prefs_t* const prefs);
+void LZ4IO_freePreferences(LZ4IO_prefs_t* prefs);
 
 /* Size in bytes of a legacy block header in little-endian format */
 #define LZIO_LEGACY_BLOCK_HEADER_SIZE 4
@@ -65,12 +65,12 @@ void LZ4IO_freePreferences(LZ4IO_prefs_t* const prefs);
 /* ************************************************** */
 
 /* if output_filename == stdoutmark, writes to stdout */
-int LZ4IO_compressFilename(LZ4IO_prefs_t* const prefs, const char* input_filename, const char* output_filename, int compressionlevel);
-int LZ4IO_decompressFilename(LZ4IO_prefs_t* const prefs, const char* input_filename, const char* output_filename);
+int LZ4IO_compressFilename(const char* input_filename, const char* output_filename, int compressionlevel, const LZ4IO_prefs_t* prefs);
+int LZ4IO_decompressFilename(const char* input_filename, const char* output_filename, const LZ4IO_prefs_t* prefs);
 
 /* if suffix == stdoutmark, writes to stdout */
-int LZ4IO_compressMultipleFilenames(LZ4IO_prefs_t* const prefs, const char** inFileNamesTable, int ifntSize, const char* suffix, int compressionlevel);
-int LZ4IO_decompressMultipleFilenames(LZ4IO_prefs_t* const prefs, const char** inFileNamesTable, int ifntSize, const char* suffix);
+int LZ4IO_compressMultipleFilenames(const char** inFileNamesTable, int ifntSize, const char* suffix, int compressionlevel, const LZ4IO_prefs_t* prefs);
+int LZ4IO_decompressMultipleFilenames(const char** inFileNamesTable, int ifntSize, const char* suffix, const LZ4IO_prefs_t* prefs);
 
 
 /* ************************************************** */