diff --git a/modules/libcom/src/misc/epicsString.c b/modules/libcom/src/misc/epicsString.c
index 951c65606..6df10c3a6 100644
--- a/modules/libcom/src/misc/epicsString.c
+++ b/modules/libcom/src/misc/epicsString.c
@@ -83,38 +83,40 @@ int epicsStrnRawFromEscaped(char *dst, size_t dstlen, const char *src,
                 if (!srclen-- || !(c = *src++)) {
                     OUT(u); goto done;
                 }
-                if (c < '0' || c > '7') {
+                if (c < '0' || c > '7' || u > 037) {
                     OUT(u); goto input;
                 }
                 u = u << 3 | (c - '0');
-
-                if (u > 0377) {
-                    /* Undefined behaviour! */
-                }
                 OUT(u);
             }
             break;
 
         case 'x' :
-            { /* \xXXX... */
+            { /* \xXX */
                 unsigned int u = 0;
 
                 if (!srclen-- || !(c = *src++ & 0xff))
                     goto done;
 
-                while (isxdigit(c)) {
-                    u = u << 4 | ((c > '9') ? toupper(c) - 'A' + 10 : c - '0');
-                    if (u > 0xff) {
-                        /* Undefined behaviour! */
-                    }
-                    if (!srclen-- || !(c = *src++ & 0xff)) {
-                        OUT(u);
-                        goto done;
-                    }
+                if (!isxdigit(c))
+                    goto input;
+
+                u = u << 4 | ((c > '9') ? toupper(c) - 'A' + 10 : c - '0');
+
+                if (!srclen-- || !(c = *src++ & 0xff)) {
+                    OUT(u);
+                    goto done;
                 }
+
+                if (!isxdigit(c)) {
+                    OUT(u);
+                    goto input;
+                }
+
+                u = u << 4 | ((c > '9') ? toupper(c) - 'A' + 10 : c - '0');
                 OUT(u);
-                goto input;
             }
+            break;
 
         default:
             OUT(c);
diff --git a/modules/libcom/test/epicsStringTest.c b/modules/libcom/test/epicsStringTest.c
index 8bd1d5baa..0f1537f97 100644
--- a/modules/libcom/test/epicsStringTest.c
+++ b/modules/libcom/test/epicsStringTest.c
@@ -88,7 +88,7 @@ MAIN(epicsStringTest)
     char *s;
     int status;
 
-    testPlan(406);
+    testPlan(416);
 
     testChars();
 
@@ -257,6 +257,19 @@ MAIN(epicsStringTest)
     testOk(result[0] == 0123, "  Octal escape (got \\%03o)", result[0]);
     testOk(result[status] == 0, "  0-terminated");
 
+    memset(result, 'x', sizeof(result));
+    status = epicsStrnRawFromEscaped(result, 4, "\\377", 4);
+    testOk(status == 1,      "raw(\"\\377\", 4) -> %d (exp. 1)", status);
+    testOk((result[0] & 0xff) == 0377, "  Octal escape (got \\%03o)", result[0]);
+    testOk(result[status] == 0, "  0-terminated");
+
+    memset(result, 'x', sizeof(result));
+    status = epicsStrnRawFromEscaped(result, 4, "\\400", 4);
+    testOk(status == 2,      "raw(\"\\400\", 4) -> %d (exp. 2)", status);
+    testOk(result[0] == 040, "  Octal escape (got \\%03o)", result[0]);
+    testOk(result[1] == '0', "  Terminator char got '%c'", result[1]);
+    testOk(result[status] == 0, "  0-terminated");
+
     memset(result, 'x', sizeof(result));
     status = epicsStrnRawFromEscaped(result, 4, "\\812", 2);
     testOk(status == 1,      "raw(\"\\812\", 2) -> %d (exp. 1)", status);
@@ -307,14 +320,17 @@ MAIN(epicsStringTest)
 
     memset(result, 'x', sizeof(result));
     status = epicsStrnRawFromEscaped(result, 4, "\\x012", 5);
-    testOk(status == 1,      "raw(\"\\x012\", 5) -> %d (exp. 1)", status);
-    testOk(result[0] == 0x12,"  Hex escape (got \\x%x)", result[0]);
+    testOk(status == 2,      "raw(\"\\x012\", 5) -> %d (exp. 2)", status);
+    testOk(result[0] == 0x1,"  Hex escape (got \\x%x)", result[0]);
+    testOk(result[1] == '2', "  Terminator char got '%c'", result[1]);
     testOk(result[status] == 0, "  0-terminated");
 
     memset(result, 'x', sizeof(result));
     status = epicsStrnRawFromEscaped(result, 4, "\\x0012", 6);
-    testOk(status == 1,      "raw(\"\\x0012\", 6) -> %d (exp. 1)", status);
-    testOk(result[0] == 0x12,"  Hex escape (got \\x%x)", result[0]);
+    testOk(status == 3,      "raw(\"\\x0012\", 6) -> %d (exp. 3)", status);
+    testOk(result[0] == 0,"  Hex escape (got \\x%x)", result[0]);
+    testOk(result[1] == '1', "  Terminator char got '%c'", result[1]);
+    testOk(result[2] == '2', "  Following char got '%c'", result[2]);
     testOk(result[status] == 0, "  0-terminated");
 
     memset(result, 'x', sizeof(result));