diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index 28f88cde..254e2923 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -444,17 +444,22 @@ typedef struct {
     unsigned long long decompressedBound;
 } ZSTD_frameSizeInfo;
 
+static ZSTD_frameSizeInfo ZSTD_errorFrameSizeInfo(size_t ret)
+{
+    ZSTD_frameSizeInfo frameSizeInfo;
+    frameSizeInfo.compressedSize = ret;
+    frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_UNKNOWN;
+    return frameSizeInfo;
+}
+
 static ZSTD_frameSizeInfo ZSTD_findFrameSizeInfo(const void* src, size_t srcSize)
 {
     ZSTD_frameSizeInfo frameSizeInfo;
     memset(&frameSizeInfo, 0, sizeof(ZSTD_frameSizeInfo));
 
 #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
-    if (ZSTD_isLegacy(src, srcSize)) {
-        frameSizeInfo.compressedSize = ZSTD_findFrameCompressedSizeLegacy(src, srcSize);
-        frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_ERROR;
-        return frameSizeInfo;
-    }
+    if (ZSTD_isLegacy(src, srcSize))
+        return ZSTD_errorFrameSizeInfo(ZSTD_findFrameCompressedSizeLegacy(src, srcSize));
 #endif
 
     if ((srcSize >= ZSTD_SKIPPABLEHEADERSIZE)
@@ -471,16 +476,10 @@ static ZSTD_frameSizeInfo ZSTD_findFrameSizeInfo(const void* src, size_t srcSize
         /* Extract Frame Header */
         {
             size_t const ret = ZSTD_getFrameHeader(&zfh, src, srcSize);
-            if (ZSTD_isError(ret)) {
-                frameSizeInfo.compressedSize = ret;
-                frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_ERROR;
-                return frameSizeInfo;
-            }
-            if (ret > 0) {
-                frameSizeInfo.compressedSize = ERROR(srcSize_wrong);
-                frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_ERROR;
-                return frameSizeInfo;
-            }
+            if (ZSTD_isError(ret))
+                return ZSTD_errorFrameSizeInfo(ret);
+            if (ret > 0)
+                return ZSTD_errorFrameSizeInfo(ERROR(srcSize_wrong));
         }
 
         ip += zfh.headerSize;
@@ -490,17 +489,11 @@ static ZSTD_frameSizeInfo ZSTD_findFrameSizeInfo(const void* src, size_t srcSize
         while (1) {
             blockProperties_t blockProperties;
             size_t const cBlockSize = ZSTD_getcBlockSize(ip, remainingSize, &blockProperties);
-            if (ZSTD_isError(cBlockSize)) {
-                frameSizeInfo.compressedSize = cBlockSize;
-                frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_ERROR;
-                return frameSizeInfo;
-            }
+            if (ZSTD_isError(cBlockSize))
+                return ZSTD_errorFrameSizeInfo(cBlockSize);
 
-            if (ZSTD_blockHeaderSize + cBlockSize > remainingSize) {
-                frameSizeInfo.compressedSize = ERROR(srcSize_wrong);
-                frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_ERROR;
-                return frameSizeInfo;
-            }
+            if (ZSTD_blockHeaderSize + cBlockSize > remainingSize)
+                return ZSTD_errorFrameSizeInfo(ERROR(srcSize_wrong));
 
             ip += ZSTD_blockHeaderSize + cBlockSize;
             remainingSize -= ZSTD_blockHeaderSize + cBlockSize;
@@ -511,11 +504,8 @@ static ZSTD_frameSizeInfo ZSTD_findFrameSizeInfo(const void* src, size_t srcSize
 
         /* Final frame content checksum */
         if (zfh.checksumFlag) {
-            if (remainingSize < 4) {
-                frameSizeInfo.compressedSize = ERROR(srcSize_wrong);
-                frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_ERROR;
-                return frameSizeInfo;
-            }
+            if (remainingSize < 4)
+                return ZSTD_errorFrameSizeInfo(ERROR(srcSize_wrong));
             ip += 4;
         }
 
@@ -534,7 +524,7 @@ static ZSTD_frameSizeInfo ZSTD_findFrameSizeInfo(const void* src, size_t srcSize
  *  @return : the compressed size of the frame starting at `src` */
 size_t ZSTD_findFrameCompressedSize(const void *src, size_t srcSize)
 {
-    ZSTD_frameSizeInfo frameSizeInfo = ZSTD_findFrameSizeInfo(src, srcSize);
+    ZSTD_frameSizeInfo const frameSizeInfo = ZSTD_findFrameSizeInfo(src, srcSize);
     return frameSizeInfo.compressedSize;
 }
 
@@ -550,9 +540,9 @@ unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize)
     unsigned long long bound = 0;
     /* Iterate over each frame */
     while (srcSize > 0) {
-        ZSTD_frameSizeInfo frameSizeInfo = ZSTD_findFrameSizeInfo(src, srcSize);
-        size_t compressedSize = frameSizeInfo.compressedSize;
-        unsigned long long decompressedBound = frameSizeInfo.decompressedBound;
+        ZSTD_frameSizeInfo const frameSizeInfo = ZSTD_findFrameSizeInfo(src, srcSize);
+        size_t const compressedSize = frameSizeInfo.compressedSize;
+        unsigned long long const decompressedBound = frameSizeInfo.decompressedBound;
         if (ZSTD_isError(compressedSize) || decompressedBound == ZSTD_CONTENTSIZE_ERROR) {
             return ZSTD_CONTENTSIZE_ERROR;
         }
diff --git a/lib/zstd.h b/lib/zstd.h
index e49a4048..182ff376 100644
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -1104,16 +1104,16 @@ typedef enum {
 ZSTDLIB_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
 
 /** ZSTD_decompressBound() :
- *  currently incompatible with legacy mode
- *  `src` must point to the start of a ZSTD frame or a skippeable frame
- *  `srcSize` must be at least as large as the frame contained
+ *  `src` should point the start of a series of ZSTD encoded and/or skippable frames
+ *  `srcSize` must be the _exact_ size of this series
+ *       (i.e. there should be a frame boundary exactly at `srcSize` bytes after `src`)
  *  @return : - the maximum decompressed size of the compressed source
  *            - if an error occured: ZSTD_CONTENTSIZE_ERROR
  *
  *  note 1  : an error can occur if `src` points to a legacy frame or an invalid/incorrectly formatted frame.
- *  note 2  : the bound is exact when Frame_Content_Size field is available in EVERY frame of `src`.
+ *  note 2  : the bound is exact when Frame_Content_Size field is available in _every_ frame of `src`.
  *  note 3  : when Frame_Content_Size isn't provided, the upper-bound for that frame is calculated by:
- *              upper-bound = min(128 KB, Window_Size)
+ *              upper-bound = # blocks * min(128 KB, Window_Size)
  *  note 4  : we always use Frame_Content_Size to bound the decompressed frame size if it's present.
  */
 ZSTDLIB_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSice);