diff --git a/src/core/marsh.c b/src/core/marsh.c
index ef22de0d..bb30eed6 100644
--- a/src/core/marsh.c
+++ b/src/core/marsh.c
@@ -916,7 +916,7 @@ static const uint8_t *unmarshal_one_fiber(
     JanetFiber **out,
     int flags) {
 
-    /* Initialize a new fiber */
+    /* Initialize a new fiber with gc friendly defaults */
     JanetFiber *fiber = janet_gcalloc(JANET_MEMORY_FIBER, sizeof(JanetFiber));
     fiber->flags = 0;
     fiber->frame = 0;
@@ -937,16 +937,16 @@ static const uint8_t *unmarshal_one_fiber(
     int32_t stacktop = 0;
 
     /* Read ints */
-    fiber->flags = readint(st, &data);
+    int32_t fiber_flags = readint(st, &data);
     frame = readnat(st, &data);
-    fiber->stackstart = readnat(st, &data);
-    fiber->stacktop = readnat(st, &data);
-    fiber->maxstack = readnat(st, &data);
+    int32_t fiber_stackstart = readnat(st, &data);
+    int32_t fiber_stacktop = readnat(st, &data);
+    int32_t fiber_maxstack = readnat(st, &data);
 
     /* Check for bad flags and ints */
-    if ((int32_t)(frame + JANET_FRAME_SIZE) > fiber->stackstart ||
-            fiber->stackstart > fiber->stacktop ||
-            fiber->stacktop > fiber->maxstack) {
+    if ((int32_t)(frame + JANET_FRAME_SIZE) > fiber_stackstart ||
+            fiber_stackstart > fiber_stacktop ||
+            fiber_stacktop > fiber_maxstack) {
         janet_panic("fiber has incorrect stack setup");
     }
 
@@ -959,7 +959,7 @@ static const uint8_t *unmarshal_one_fiber(
 
     /* get frames */
     stack = frame;
-    stacktop = fiber->stackstart - JANET_FRAME_SIZE;
+    stacktop = fiber_stackstart - JANET_FRAME_SIZE;
     while (stack > 0) {
         JanetFunction *func = NULL;
         JanetFuncDef *def = NULL;
@@ -1028,25 +1028,31 @@ static const uint8_t *unmarshal_one_fiber(
     }
 
     /* Check for fiber env */
-    if (fiber->flags & JANET_FIBER_FLAG_HASENV) {
+    if (fiber_flags & JANET_FIBER_FLAG_HASENV) {
         Janet envv;
-        fiber->flags &= ~JANET_FIBER_FLAG_HASENV;
+        fiber_flags &= ~JANET_FIBER_FLAG_HASENV;
         data = unmarshal_one(st, data, &envv, flags + 1);
         janet_asserttype(envv, JANET_TABLE);
         fiber->env = janet_unwrap_table(envv);
     }
 
     /* Check for child fiber */
-    if (fiber->flags & JANET_FIBER_FLAG_HASCHILD) {
+    if (fiber_flags & JANET_FIBER_FLAG_HASCHILD) {
         Janet fiberv;
-        fiber->flags &= ~JANET_FIBER_FLAG_HASCHILD;
+        fiber_flags &= ~JANET_FIBER_FLAG_HASCHILD;
         data = unmarshal_one(st, data, &fiberv, flags + 1);
         janet_asserttype(fiberv, JANET_FIBER);
         fiber->child = janet_unwrap_fiber(fiberv);
     }
 
-    /* Return data */
+    /* We have valid fiber, finally construct remaining fields. */
     fiber->frame = frame;
+    fiber->flags = fiber_flags;
+    fiber->stackstart = fiber_stackstart;
+    fiber->stacktop = fiber_stacktop;
+    fiber->maxstack = fiber_maxstack;
+
+    /* Return data */
     *out = fiber;
     return data;
 }
diff --git a/test/suite8.janet b/test/suite8.janet
index 2ab968a4..b2b51740 100644
--- a/test/suite8.janet
+++ b/test/suite8.janet
@@ -216,10 +216,15 @@
 (assert-error "unmarshal errors 4"
               (unmarshal
                 @"\xD7\xCD\0e/p\x98\0\0\x03\x01\x01\x01\x02\0\0\x04\0\xCEe/p../tools
-                \0\0\0/afl\0\0\x01\0erate\xDE\xDE\xDE\xDE\xDE\xDE\xDE\xDE\xDE\xDE
-                \xA8\xDE\xDE\xDE\xDE\xDE\xDE\0\0\0\xDE\xDE_unmarshal_testcase3.ja
-                neldb\0\0\0\xD8\x05printG\x01\0\xDE\xDE\xDE'\x03\0marshal_tes/\x02
-                \0\0\0\0\0*\xFE\x01\04\x02\0\0'\x03\0\r\0\r\0\r\0\r" load-image-dict))
+\0\0\0/afl\0\0\x01\0erate\xDE\xDE\xDE\xDE\xDE\xDE\xDE\xDE\xDE\xDE
+\xA8\xDE\xDE\xDE\xDE\xDE\xDE\0\0\0\xDE\xDE_unmarshal_testcase3.ja
+neldb\0\0\0\xD8\x05printG\x01\0\xDE\xDE\xDE'\x03\0marshal_tes/\x02
+\0\0\0\0\0*\xFE\x01\04\x02\0\0'\x03\0\r\0\r\0\r\0\r" load-image-dict))
 
+# No segfault, valgrind clean.
+(def x @"\xCC\xCD.nd\x80\0\r\x1C\xCDg!\0\x07\xCC\xCD\r\x1Ce\x10\0\r;\xCDb\x04\xFF9\xFF\x80\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04uu\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\0\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04}\x04\x04\x04\x04\x04\x04\x04\x04#\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\0\x01\0\0\x03\x04\x04\x04\xE2\x03\x04\x04\x04\x04\x04\x04\x04\x04\x04\x14\x1A\x04\x04\x04\x04\x04\x18\x04\x04!\x04\xE2\x03\x04\x04\x04\x04\x04\x04$\x04\x04\x04\x04\x04\x04\x04\x04\x04\x80\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04\x04A\0\0\0\x03\0\0!\xBF\xFF")
+(unmarshal x load-image-dict)
+(gccollect)
+(marshal x make-image-dict)
 
 (end-suite)