diff --git a/src/jemalloc.c b/src/jemalloc.c
index df0c1ebc..ccb20c81 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -865,6 +865,14 @@ malloc_conf_multi_sizes_next(const char **slab_size_segment_cur,
 	return false;
 }
 
+static void
+malloc_conf_format_error(const char *msg, const char *begin, const char *end) {
+	size_t len = end - begin + 1;
+	len = len > BUFERROR_BUF ? BUFERROR_BUF : len;
+
+	malloc_printf("<jemalloc>: %s -- %.*s\n", msg, (int)len, begin);
+}
+
 static bool
 malloc_conf_next(char const **opts_p, char const **k_p, size_t *klen_p,
     char const **v_p, size_t *vlen_p) {
@@ -898,13 +906,15 @@ malloc_conf_next(char const **opts_p, char const **k_p, size_t *klen_p,
 			break;
 		case '\0':
 			if (opts != *opts_p) {
-				malloc_write("<jemalloc>: Conf string ends "
-				    "with key\n");
+				malloc_conf_format_error(
+				    "Conf string ends with key",
+				    *opts_p, opts - 1);
 				had_conf_error = true;
 			}
 			return true;
 		default:
-			malloc_write("<jemalloc>: Malformed conf string\n");
+			malloc_conf_format_error(
+			    "Malformed conf string", *opts_p, opts);
 			had_conf_error = true;
 			return true;
 		}
@@ -922,8 +932,9 @@ malloc_conf_next(char const **opts_p, char const **k_p, size_t *klen_p,
 			 * comma if one exists.
 			 */
 			if (*opts == '\0') {
-				malloc_write("<jemalloc>: Conf string ends "
-				    "with comma\n");
+				malloc_conf_format_error(
+				    "Conf string ends with comma",
+				    *opts_p, opts - 1);
 				had_conf_error = true;
 			}
 			*vlen_p = (uintptr_t)opts - 1 - (uintptr_t)*v_p;