diff --git a/src/regexp.c b/src/regexp.c
index dc0433d..9ce4cd8 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -583,6 +583,7 @@
 #endif
 static char_u	*regcode;	/* Code-emit pointer, or JUST_CALC_SIZE */
 static long	regsize;	/* Code size. */
+static int	reg_toolong;	/* TRUE when offset out of range */
 static char_u	had_endbrace[NSUBEXP];	/* flags, TRUE if end of () found */
 static unsigned	regflags;	/* RF_ flags for prog */
 static long	brace_min[10];	/* Minimums for complex brace repeats */
@@ -1028,9 +1029,11 @@
     regcomp_start(expr, re_flags);
     regcode = r->program;
     regc(REGMAGIC);
-    if (reg(REG_NOPAREN, &flags) == NULL)
+    if (reg(REG_NOPAREN, &flags) == NULL || reg_toolong)
     {
 	vim_free(r);
+	if (reg_toolong)
+	    EMSG_RET_NULL(_("E339: Pattern too long"));
 	return NULL;
     }
 
@@ -1141,6 +1144,7 @@
     re_has_z = 0;
 #endif
     regsize = 0L;
+    reg_toolong = FALSE;
     regflags = 0;
 #if defined(FEAT_SYN_HL) || defined(PROTO)
     had_eol = FALSE;
@@ -1228,7 +1232,7 @@
     {
 	skipchr();
 	br = regbranch(&flags);
-	if (br == NULL)
+	if (br == NULL || reg_toolong)
 	    return NULL;
 	regtail(ret, br);	/* BRANCH -> BRANCH. */
 	if (!(flags & HASWIDTH))
@@ -1313,6 +1317,8 @@
 	    break;
 	skipchr();
 	regtail(latest, regnode(END)); /* operand ends */
+	if (reg_toolong)
+	    break;
 	reginsert(MATCH, latest);
 	chain = latest;
     }
@@ -1382,7 +1388,7 @@
 			    break;
 	    default:
 			    latest = regpiece(&flags);
-			    if (latest == NULL)
+			    if (latest == NULL || reg_toolong)
 				return NULL;
 			    *flagp |= flags & (HASWIDTH | HASNL | HASLOOKBH);
 			    if (chain == NULL)	/* First piece. */
@@ -2540,8 +2546,16 @@
 	offset = (int)(scan - val);
     else
 	offset = (int)(val - scan);
-    *(scan + 1) = (char_u) (((unsigned)offset >> 8) & 0377);
-    *(scan + 2) = (char_u) (offset & 0377);
+    /* When the offset uses more than 16 bits it can no longer fit in the two
+     * bytes avaliable.  Use a global flag to avoid having to check return
+     * values in too many places. */
+    if (offset > 0xffff)
+	reg_toolong = TRUE;
+    else
+    {
+	*(scan + 1) = (char_u) (((unsigned)offset >> 8) & 0377);
+	*(scan + 2) = (char_u) (offset & 0377);
+    }
 }
 
 /*
@@ -5764,6 +5778,8 @@
 
 /*
  * regnext - dig the "next" pointer out of a node
+ * Returns NULL when calculating size, when there is no next item and when
+ * there is an error.
  */
     static char_u *
 regnext(p)
@@ -5771,7 +5787,7 @@
 {
     int	    offset;
 
-    if (p == JUST_CALC_SIZE)
+    if (p == JUST_CALC_SIZE || reg_toolong)
 	return NULL;
 
     offset = NEXT(p);