diff --git a/src/backend/regex/regc_color.c b/src/backend/regex/regc_color.c
index 1c60566..e6aa899 100644
--- a/src/backend/regex/regc_color.c
+++ b/src/backend/regex/regc_color.c
@@ -247,7 +247,15 @@ newcolor(struct colormap * cm)
 		/* oops, must allocate more */
 		struct colordesc *newCd;
 
+		if (cm->max == MAX_COLOR)
+		{
+			CERR(REG_ECOLORS);
+			return COLORLESS;	/* too many colors */
+		}
+
 		n = cm->ncds * 2;
+		if (n > MAX_COLOR + 1)
+			n = MAX_COLOR + 1;
 		if (cm->cd == cm->cdspace)
 		{
 			newCd = (struct colordesc *) MALLOC(n * sizeof(struct colordesc));
diff --git a/src/include/regex/regerrs.h b/src/include/regex/regerrs.h
index a761371..6516d7e 100644
--- a/src/include/regex/regerrs.h
+++ b/src/include/regex/regerrs.h
@@ -77,3 +77,7 @@
 {
 	REG_ETOOBIG, "REG_ETOOBIG", "nfa has too many states"
 },
+
+{
+	REG_ECOLORS, "REG_ECOLORS", "too many distinct characters in regex"
+},
diff --git a/src/include/regex/regex.h b/src/include/regex/regex.h
index 616c2c6..a7fb14f 100644
--- a/src/include/regex/regex.h
+++ b/src/include/regex/regex.h
@@ -153,6 +153,7 @@ typedef struct
 #define REG_MIXED	17			/* character widths of regex and string differ */
 #define REG_BADOPT	18			/* invalid embedded option */
 #define REG_ETOOBIG 19			/* nfa has too many states */
+#define REG_ECOLORS 20			/* too many distinct characters in regex */
 /* two specials for debugging and testing */
 #define REG_ATOI	101			/* convert error-code name to number */
 #define REG_ITOA	102			/* convert error-code number to name */
diff --git a/src/include/regex/regguts.h b/src/include/regex/regguts.h
index e1e406f..fc7f5ae 100644
--- a/src/include/regex/regguts.h
+++ b/src/include/regex/regguts.h
@@ -148,6 +148,7 @@
 typedef short color;			/* colors of characters */
 typedef int pcolor;				/* what color promotes to */
 
+#define MAX_COLOR	32767		/* max value that fits in 'color' datatype */
 #define COLORLESS	(-1)		/* impossible color */
 #define WHITE		0			/* default color, parent of all others */