diff --git a/doc/zstd_manual.html b/doc/zstd_manual.html
index 4d5df597..360a6e77 100644
--- a/doc/zstd_manual.html
+++ b/doc/zstd_manual.html
@@ -718,7 +718,8 @@ size_t ZSTD_CDict_loadDictionary(ZSTD_CDict* cdict, const void* dict, size_t dic
  @return : pointer to ZSTD_DCtx*, or NULL if error (size too small)
   Note : zstd will never resize nor malloc() when using a static dctx.
          If it needs more memory than available, it will simply error out.
-  Note 2 : there is no corresponding "free" function.
+  Note 2 : static dctx is incompatible with legacy support
+  Note 3 : there is no corresponding "free" function.
            Since workspace was allocated externally, it must be freed externally.
   Limitation : currently not compatible with internal DDict creation,
                such as ZSTD_initDStream_usingDict().
diff --git a/lib/compress/zstdmt_compress.c b/lib/compress/zstdmt_compress.c
index fc7f52a2..0c6bc724 100644
--- a/lib/compress/zstdmt_compress.c
+++ b/lib/compress/zstdmt_compress.c
@@ -271,6 +271,7 @@ _endJob:
 
 struct ZSTDMT_CCtx_s {
     POOL_ctx* factory;
+    ZSTDMT_jobDescription* jobs;
     ZSTDMT_bufferPool* buffPool;
     ZSTDMT_CCtxPool* cctxPool;
     pthread_mutex_t jobCompleted_mutex;
@@ -294,10 +295,9 @@ struct ZSTDMT_CCtx_s {
     size_t sectionSize;
     ZSTD_CDict* cdict;
     ZSTD_CStream* cstream;
-    ZSTDMT_jobDescription jobs[1];   /* variable size (must lies at the end) */
 };
 
-ZSTDMT_CCtx *ZSTDMT_createCCtx(unsigned nbThreads)
+ZSTDMT_CCtx* ZSTDMT_createCCtx(unsigned nbThreads)
 {
     ZSTDMT_CCtx* cctx;
     U32 const minNbJobs = nbThreads + 2;
@@ -306,7 +306,7 @@ ZSTDMT_CCtx *ZSTDMT_createCCtx(unsigned nbThreads)
     DEBUGLOG(5, "nbThreads : %u  ; minNbJobs : %u ;  nbJobsLog2 : %u ;  nbJobs : %u  \n",
             nbThreads, minNbJobs, nbJobsLog2, nbJobs);
     if ((nbThreads < 1) | (nbThreads > ZSTDMT_NBTHREADS_MAX)) return NULL;
-    cctx = (ZSTDMT_CCtx*) calloc(1, sizeof(ZSTDMT_CCtx) + nbJobs*sizeof(ZSTDMT_jobDescription));
+    cctx = (ZSTDMT_CCtx*) calloc(1, sizeof(ZSTDMT_CCtx));
     if (!cctx) return NULL;
     cctx->nbThreads = nbThreads;
     cctx->jobIDMask = nbJobs - 1;
@@ -314,9 +314,10 @@ ZSTDMT_CCtx *ZSTDMT_createCCtx(unsigned nbThreads)
     cctx->sectionSize = 0;
     cctx->overlapRLog = 3;
     cctx->factory = POOL_create(nbThreads, 1);
+    cctx->jobs = (ZSTDMT_jobDescription*) malloc(nbJobs * sizeof(*cctx->jobs));
     cctx->buffPool = ZSTDMT_createBufferPool(nbThreads);
     cctx->cctxPool = ZSTDMT_createCCtxPool(nbThreads);
-    if (!cctx->factory | !cctx->buffPool | !cctx->cctxPool) {  /* one object was not created */
+    if (!cctx->factory | !cctx->jobs | !cctx->buffPool | !cctx->cctxPool) {
         ZSTDMT_freeCCtx(cctx);
         return NULL;
     }
@@ -356,6 +357,7 @@ size_t ZSTDMT_freeCCtx(ZSTDMT_CCtx* mtctx)
     POOL_free(mtctx->factory);
     if (!mtctx->allJobsCompleted) ZSTDMT_releaseAllJobResources(mtctx); /* stop workers first */
     ZSTDMT_freeBufferPool(mtctx->buffPool);  /* release job resources into pools first */
+    free(mtctx->jobs);
     ZSTDMT_freeCCtxPool(mtctx->cctxPool);
     ZSTD_freeCDict(mtctx->cdict);
     ZSTD_freeCStream(mtctx->cstream);
@@ -491,7 +493,8 @@ size_t ZSTDMT_compressCCtx(ZSTDMT_CCtx* mtctx,
 /* =======      Streaming API     ======= */
 /* ====================================== */
 
-static void ZSTDMT_waitForAllJobsCompleted(ZSTDMT_CCtx* zcs) {
+static void ZSTDMT_waitForAllJobsCompleted(ZSTDMT_CCtx* zcs)
+{
     while (zcs->doneJobID < zcs->nextJobID) {
         unsigned const jobID = zcs->doneJobID & zcs->jobIDMask;
         PTHREAD_MUTEX_LOCK(&zcs->jobCompleted_mutex);
diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index fe7446ab..a5972438 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -1586,6 +1586,8 @@ static size_t ZSTD_decompressMultiFrame(ZSTD_DCtx* dctx,
             size_t decodedSize;
             size_t const frameSize = ZSTD_findFrameCompressedSizeLegacy(src, srcSize);
             if (ZSTD_isError(frameSize)) return frameSize;
+            /* legacy support is incompatible with static dctx */
+            if (dctx->staticSize) return ERROR(memory_allocation);
 
             decodedSize = ZSTD_decompressLegacy(dst, dstCapacity, src, frameSize, dict, dictSize);
 
@@ -2258,8 +2260,11 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inB
     U32 someMoreWork = 1;
 
 #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
-    if (zds->legacyVersion)
+    if (zds->legacyVersion) {
+        /* legacy support is incompatible with static dctx */
+        if (zds->staticSize) return ERROR(memory_allocation);
         return ZSTD_decompressLegacyStream(zds->legacyContext, zds->legacyVersion, output, input);
+    }
 #endif
 
     while (someMoreWork) {
@@ -2277,6 +2282,8 @@ size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inB
                     if (legacyVersion) {
                         const void* const dict = zds->ddict ? zds->ddict->dictContent : NULL;
                         size_t const dictSize = zds->ddict ? zds->ddict->dictSize : 0;
+                        /* legacy support is incompatible with static dctx */
+                        if (zds->staticSize) return ERROR(memory_allocation);
                         CHECK_F(ZSTD_initLegacyStream(&zds->legacyContext, zds->previousLegacyVersion, legacyVersion,
                                                        dict, dictSize));
                         zds->legacyVersion = zds->previousLegacyVersion = legacyVersion;
diff --git a/lib/zstd.h b/lib/zstd.h
index bc3d7a0e..d3a4d178 100644
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -844,7 +844,8 @@ ZSTDLIB_API ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem);
  * @return : pointer to ZSTD_DCtx*, or NULL if error (size too small)
  *  Note : zstd will never resize nor malloc() when using a static dctx.
  *         If it needs more memory than available, it will simply error out.
- *  Note 2 : there is no corresponding "free" function.
+ *  Note 2 : static dctx is incompatible with legacy support
+ *  Note 3 : there is no corresponding "free" function.
  *           Since workspace was allocated externally, it must be freed externally.
  *  Limitation : currently not compatible with internal DDict creation,
  *               such as ZSTD_initDStream_usingDict().