diff --git a/collects/tests/mzscheme/benchmarks/rx/auto.ss b/collects/tests/mzscheme/benchmarks/rx/auto.ss
index 69f04f747e..c74befa265 100755
--- a/collects/tests/mzscheme/benchmarks/rx/auto.ss
+++ b/collects/tests/mzscheme/benchmarks/rx/auto.ss
@@ -195,6 +195,12 @@ exec mzscheme -qu "$0" ${1+"$@"}
       (list 'escape #"noBABthe AAABquickAAAB brown foxAB" #"noB(?:[^AB]+|A.)*B" 10 '())
       (list 'escape #"yesbabthe aaabquickaaab frown foxabb" #"(?i:yesB(?:[^AB]+|A.)*B)" 100000 '(rxmzold))
       (list 'escape #"nobabthe aaabquickaaab frown foxab" #"(?i:noB(?:[^AB]+|A.)*B)" 10 '(rxmzold))
+      (list 'backtrack1 (make-bytes 1000 (char->integer #\x)) #".*z" 100 '())
+      (list 'backtrack1z (bytes-append #"z" (make-bytes 1000 (char->integer #\x))) #".*z" 100 '())
+      (list 'backtrack2 (make-bytes 1000 (char->integer #\x))  #".*(z)" 100 '())
+      (list 'backtrack2z (bytes-append #"z" (make-bytes 1000 (char->integer #\x)))  #".*(z)" 100 '())
+      (list 'backtrack3 (make-bytes 1000 (char->integer #\x))  #".*(?:z)" 100 '())
+      (list 'backtrack3z (bytes-append #"z" (make-bytes 1000 (char->integer #\x)))  #".*(?:z)" 100 '())
       (list 'stress-same (make-bytes 1000 (char->integer #\x)) #"^(x|a)\\1*x$" 1000 '(rxmzold))
       (list 'stress-same (make-bytes 1000 (char->integer #\x)) #"^(x*|a)\\1x$" 1000 '(rxmzold))
       (list 'stress-same (make-bytes 1000 (char->integer #\x)) #"^(x*?|a)\\1x$" 1000 '(rxmzold))
diff --git a/src/mzscheme/src/regexp.c b/src/mzscheme/src/regexp.c
index 81706e2ea9..dc59acbc9d 100644
--- a/src/mzscheme/src/regexp.c
+++ b/src/mzscheme/src/regexp.c
@@ -249,21 +249,40 @@ regcomp(char *expstr, rxpos exp, int explen, int pcre)
       longest_is_ci = 0;
       len = 0;
       for (; scan != 0; scan = regnext(scan)) {
-	if (((rOP(scan) == EXACTLY) || (rOP(scan) == EXACTLY_CI))
-	    && rOPLEN(OPERAND(scan)) >= len) {
-	  /* Skip regmust if it contains a null character: */
-	  rxpos ls = OPSTR(OPERAND(scan));
-	  int ll = rOPLEN(OPERAND(scan)), i;
-	  for (i = 0; i < ll; i++) {
-	    if (!regstr[ls + i])
-	      break;
-	  }
-	  if (i >= ll) {
-	    longest = ls;
-	    len = ll;
-	    longest_is_ci = (rOP(scan) == EXACTLY_CI);
-	  }
-	}
+        int mscan = scan;
+        while (1) {
+          int mop;
+          mop = rOP(mscan);
+          if (((mop == EXACTLY) || (mop == EXACTLY_CI))
+              && rOPLEN(OPERAND(mscan)) >= len) {
+            /* Skip regmust if it contains a null character: */
+            rxpos ls = OPSTR(OPERAND(mscan));
+            int ll = rOPLEN(OPERAND(mscan)), i;
+            for (i = 0; i < ll; i++) {
+              if (!regstr[ls + i])
+                break;
+            }
+            if (i >= ll) {
+              longest = ls;
+              len = ll;
+              longest_is_ci = (rOP(mscan) == EXACTLY_CI);
+            }
+            break;
+          } else if ((mop == EXACTLY1) && (1 >= len)) {
+            /* Skip if it's a null character */
+            if (regstr[OPERAND(mscan)]) {
+              longest = OPERAND(mscan);
+              len = 1;
+              longest_is_ci = 0;
+            }
+            break;
+          } else if ((mop == OPENN) 
+                     || (mop == SAVECONST)
+                     || ((mop >= OPEN) && (mop < CLOSE))) {
+            mscan = NEXT_OP(mscan);
+          } else
+            break;
+        }
       }
       if (longest) {
 	r->regmust = longest;