diff --git a/js/src/jsemit.h b/js/src/jsemit.h
index f1e7272db5ec..b00874d17871 100644
--- a/js/src/jsemit.h
+++ b/js/src/jsemit.h
@@ -478,12 +478,20 @@ js_SetSrcNoteOffset(JSContext *cx, JSCodeGenerator *cg, uintN index,
  * the CG_COUNT_FINAL_SRCNOTES macro.  This macro knows a lot about details of
  * js_FinishTakingSrcNotes.
  */
-#define CG_COUNT_FINAL_SRCNOTES(cg)                                           \
-    ((cg)->prolog.noteCount +                                                 \
-     (((cg)->prolog.noteCount && (cg)->prolog.currentLine != (cg)->firstLine) \
-      ? 2 + (((cg)->firstLine > SN_3BYTE_OFFSET_MASK) << 1)                   \
-      : 0) +                                                                  \
-     (cg)->main.noteCount + 1)
+#define CG_COUNT_FINAL_SRCNOTES(cg, cnt)                                      \
+    JS_BEGIN_MACRO                                                            \
+        cnt = (cg)->main.noteCount + 1;                                       \
+        if ((cg)->prolog.noteCount) {                                         \
+            cnt += (cg)->prolog.noteCount;                                    \
+            if ((cg)->prolog.currentLine != (cg)->firstLine) {                \
+                ptrdiff_t diff_ = CG_PROLOG_OFFSET(cg) -                      \
+                                  (cg)->prolog.lastNoteOffset;                \
+                if (diff_ > SN_DELTA_MASK)                                    \
+                    cnt += JS_HOWMANY(diff_ - SN_DELTA_MASK, SN_XDELTA_MASK); \
+                cnt += 2 + (((cg)->firstLine > SN_3BYTE_OFFSET_MASK) << 1);   \
+            }                                                                 \
+        }                                                                     \
+    JS_END_MACRO
 
 extern JSBool
 js_FinishTakingSrcNotes(JSContext *cx, JSCodeGenerator *cg, jssrcnote *notes);
@@ -509,10 +517,12 @@ js_NewTryNote(JSContext *cx, JSCodeGenerator *cg, ptrdiff_t start,
  * preallocate enough space in a JSTryNote[] to pass as the notes parameter of
  * js_FinishTakingTryNotes.
  */
-#define CG_COUNT_FINAL_TRYNOTES(cg)                                           \
-    (((cg)->tryNext > (cg)->tryBase)                                          \
-     ? PTRDIFF(cg->tryNext, cg->tryBase, JSTryNote) + 1                       \
-     : 0)
+#define CG_COUNT_FINAL_TRYNOTES(cg, cnt)                                      \
+    JS_BEGIN_MACRO                                                            \
+        cnt = ((cg)->tryNext > (cg)->tryBase)                                 \
+              ? PTRDIFF(cg->tryNext, cg->tryBase, JSTryNote) + 1              \
+              : 0;                                                            \
+    JS_END_MACRO
 
 extern void
 js_FinishTakingTryNotes(JSContext *cx, JSCodeGenerator *cg, JSTryNote *notes);
diff --git a/js/src/jsscript.c b/js/src/jsscript.c
index adaaf14a3bf9..fb9bd025de39 100644
--- a/js/src/jsscript.c
+++ b/js/src/jsscript.c
@@ -510,11 +510,11 @@ js_XDRScript(JSXDRState *xdr, JSScript **scriptp, JSBool *hasMagic)
 
             if (ntrynotes)
                 nsrcnotes += JSTRYNOTE_ALIGNMASK;
-            newscript = JS_realloc(cx, script,
-                                   sizeof(JSScript) +
-                                   length * sizeof(jsbytecode) +
-                                   nsrcnotes * sizeof(jssrcnote) +
-                                   ntrynotes * sizeof(JSTryNote));
+            newscript = (JSScript *) JS_realloc(cx, script,
+                                                sizeof(JSScript) +
+                                                length * sizeof(jsbytecode) +
+                                                nsrcnotes * sizeof(jssrcnote) +
+                                                ntrynotes * sizeof(JSTryNote));
             if (!newscript)
                 goto error;
 
@@ -989,8 +989,8 @@ js_NewScript(JSContext *cx, uint32 length, uint32 nsrcnotes, uint32 ntrynotes)
     JSScript *script;
 
     /* Round up source note count to align script->trynotes for its type. */
-    /* XXX only if ntrynotes != 0, but then tinderbox tests crash */
-    nsrcnotes += JSTRYNOTE_ALIGNMASK;
+    if (ntrynotes)
+        nsrcnotes += JSTRYNOTE_ALIGNMASK;
     script = (JSScript *) JS_malloc(cx,
                                     sizeof(JSScript) +
                                     length * sizeof(jsbytecode) +
@@ -1013,16 +1013,15 @@ js_NewScript(JSContext *cx, uint32 length, uint32 nsrcnotes, uint32 ntrynotes)
 JS_FRIEND_API(JSScript *)
 js_NewScriptFromCG(JSContext *cx, JSCodeGenerator *cg, JSFunction *fun)
 {
-    uint32 mainLength, prologLength;
+    uint32 mainLength, prologLength, nsrcnotes, ntrynotes;
     JSScript *script;
     const char *filename;
 
     mainLength = CG_OFFSET(cg);
     prologLength = CG_PROLOG_OFFSET(cg);
-    script = js_NewScript(cx,
-                          prologLength + mainLength,
-                          CG_COUNT_FINAL_SRCNOTES(cg),
-                          CG_COUNT_FINAL_TRYNOTES(cg));
+    CG_COUNT_FINAL_SRCNOTES(cg, nsrcnotes);
+    CG_COUNT_FINAL_TRYNOTES(cg, ntrynotes);
+    script = js_NewScript(cx, prologLength + mainLength, nsrcnotes, ntrynotes);
     if (!script)
         return NULL;