diff --git a/c/lib/mlrutil.c b/c/lib/mlrutil.c
index 61b950e15..026ec9051 100644
--- a/c/lib/mlrutil.c
+++ b/c/lib/mlrutil.c
@@ -513,3 +513,38 @@ char* regex_sub(char* input, regex_t* pregex, string_builder_t* psb, char* repla
 		return sb_finish(psb);
 	}
 }
+
+char* regex_gsub(char* input, regex_t* pregex, string_builder_t* psb, char* replacement) {
+	const size_t nmatch = 1; // xxx temp: parameterize after adding capture-group support
+	regmatch_t pmatch[nmatch];
+
+	int   match_start = 0;
+	char* current_input = input;
+
+	while (TRUE) {
+		int matched = regmatch_or_die(pregex, &current_input[match_start], nmatch, pmatch);
+		if (!matched) {
+			return current_input;
+		}
+
+		int so = pmatch[0].rm_so;
+		int eo = pmatch[0].rm_eo;
+
+		int  len1 = match_start + so;
+		int olen2 = eo - so;
+		int nlen2 = strlen(replacement);
+		int  len3 = strlen(&current_input[len1 + olen2]);
+		int  len4 = len1 + nlen2 + len3;
+
+		char* current_output = mlr_malloc_or_die(len4 + 1);
+		strncpy(&current_output[0],    current_input, len1);
+		strncpy(&current_output[len1], replacement, nlen2);
+		strncpy(&current_output[len1+nlen2], &current_input[len1+olen2], len3);
+		current_output[len4] = 0;
+
+		free(current_input);
+		current_input = current_output;
+
+		match_start = len1 + nlen2;
+	}
+}
diff --git a/c/lib/mlrutil.h b/c/lib/mlrutil.h
index e43a910dd..60ee9359d 100644
--- a/c/lib/mlrutil.h
+++ b/c/lib/mlrutil.h
@@ -135,6 +135,7 @@ int regmatch_or_die(const regex_t* pregex, const char* restrict match_string,
 // allocated.  If not, input is returned.  So in either case, the caller should
 // free the return value, and it is assumed that the input has been dynamically
 // allocated.
-char* regex_sub(char* input, regex_t* pregex, string_builder_t* psb, char* replacement);
+char*  regex_sub(char* input, regex_t* pregex, string_builder_t* psb, char* replacement);
+char* regex_gsub(char* input, regex_t* pregex, string_builder_t* psb, char* replacement);
 
 #endif // MLRUTIL_H
diff --git a/c/mapping/mlr_val.c b/c/mapping/mlr_val.c
index 38fa74046..3ba7144aa 100644
--- a/c/mapping/mlr_val.c
+++ b/c/mapping/mlr_val.c
@@ -203,7 +203,6 @@ mv_t sub_no_precomp_func(mv_t* pval1, mv_t* pval2, mv_t* pval3) {
 // *  len4 = 6 = 2+3+1
 
 mv_t sub_precomp_func(mv_t* pval1, regex_t* pregex, string_builder_t* psb, mv_t* pval3) {
-
 	char* input = pval1->u.strv;
 	char* output = regex_sub(input, pregex, psb, pval3->u.strv);
 
@@ -238,39 +237,11 @@ mv_t gsub_no_precomp_func(mv_t* pval1, mv_t* pval2, mv_t* pval3) {
 }
 
 mv_t gsub_precomp_func(mv_t* pval1, regex_t* pregex, string_builder_t* psb, mv_t* pval3) {
-	const size_t nmatch = 1; // xxx temp: parameterize after adding capture-group support
-	regmatch_t pmatch[nmatch];
+	char* input = pval1->u.strv;
+	char* output = regex_gsub(input, pregex, psb, pval3->u.strv);
 
-	int   match_start = 0;
-	char* current_input = pval1->u.strv;
-
-	while (TRUE) {
-		int matched = regmatch_or_die(pregex, &current_input[match_start], nmatch, pmatch);
-		if (!matched) {
-			free(pval3->u.strv);
-			return (mv_t) {.type = MT_STRING, .u.strv = current_input};
-		}
-
-		int so = pmatch[0].rm_so;
-		int eo = pmatch[0].rm_eo;
-
-		int  len1 = match_start + so;
-		int olen2 = eo - so;
-		int nlen2 = strlen(pval3->u.strv);
-		int  len3 = strlen(&current_input[len1 + olen2]);
-		int  len4 = len1 + nlen2 + len3;
-
-		char* current_output = mlr_malloc_or_die(len4 + 1);
-		strncpy(&current_output[0],    current_input, len1);
-		strncpy(&current_output[len1], pval3->u.strv, nlen2);
-		strncpy(&current_output[len1+nlen2], &current_input[len1+olen2], len3);
-		current_output[len4] = 0;
-
-		free(current_input);
-		current_input = current_output;
-
-		match_start = len1 + nlen2;
-	}
+	free(pval3->u.strv);
+	return (mv_t) {.type = MT_STRING, .u.strv = output};
 }
 
 // ----------------------------------------------------------------