diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index 47b5f42c..88869d82 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -878,7 +878,12 @@ size_t ZSTD_execSequence(BYTE* op,
             op = oLitEnd + length1;
             sequence.matchLength -= length1;
             match = base;
+            if (op > oend_w) {
+              memmove(op, match, sequence.matchLength);
+              return sequenceLength;
+            }
     }   }
+    /* Requirement: op <= oend_w */
 
     /* match within prefix */
     if (sequence.offset < 8) {
diff --git a/lib/legacy/zstd_v04.c b/lib/legacy/zstd_v04.c
index c9dcb94e..05e40aac 100644
--- a/lib/legacy/zstd_v04.c
+++ b/lib/legacy/zstd_v04.c
@@ -3107,8 +3107,13 @@ static size_t ZSTD_execSequence(BYTE* op,
             op = oLitEnd + length1;
             sequence.matchLength -= length1;
             match = base;
+            if (op > oend_8) {
+              memmove(op, match, sequence.matchLength);
+              return sequenceLength;
+            }
         }
     }
+    /* Requirement: op <= oend_8 */
 
     /* match within prefix */
     if (sequence.offset < 8)
diff --git a/lib/legacy/zstd_v05.c b/lib/legacy/zstd_v05.c
index 5027e2b8..96ffceb9 100644
--- a/lib/legacy/zstd_v05.c
+++ b/lib/legacy/zstd_v05.c
@@ -3312,7 +3312,12 @@ static size_t ZSTDv05_execSequence(BYTE* op,
             op = oLitEnd + length1;
             sequence.matchLength -= length1;
             match = base;
+            if (op > oend_8) {
+              memmove(op, match, sequence.matchLength);
+              return sequenceLength;
+            }
     }   }
+    /* Requirement: op <= oend_8 */
 
     /* match within prefix */
     if (sequence.offset < 8) {
diff --git a/lib/legacy/zstd_v06.c b/lib/legacy/zstd_v06.c
index d9e89f80..96a84d3e 100644
--- a/lib/legacy/zstd_v06.c
+++ b/lib/legacy/zstd_v06.c
@@ -3466,7 +3466,12 @@ size_t ZSTDv06_execSequence(BYTE* op,
             op = oLitEnd + length1;
             sequence.matchLength -= length1;
             match = base;
+            if (op > oend_8) {
+              memmove(op, match, sequence.matchLength);
+              return sequenceLength;
+            }
     }   }
+    /* Requirement: op <= oend_8 */
 
     /* match within prefix */
     if (sequence.offset < 8) {
diff --git a/lib/legacy/zstd_v07.c b/lib/legacy/zstd_v07.c
index f4c8073f..62285238 100644
--- a/lib/legacy/zstd_v07.c
+++ b/lib/legacy/zstd_v07.c
@@ -3690,7 +3690,12 @@ size_t ZSTDv07_execSequence(BYTE* op,
             op = oLitEnd + length1;
             sequence.matchLength -= length1;
             match = base;
+            if (op > oend_w) {
+              memmove(op, match, sequence.matchLength);
+              return sequenceLength;
+            }
     }   }
+    /* Requirement: op <= oend_w */
 
     /* match within prefix */
     if (sequence.offset < 8) {