diff --git a/common/format-output.c b/common/format-output.c
index f0ec81fe..c194a23c 100644
--- a/common/format-output.c
+++ b/common/format-output.c
@@ -56,15 +56,14 @@ static void fmt_indent2(int indent)
 
 static void fmt_error(struct format_ctx *fctx)
 {
-	printf("INTERNAL ERROR: formatting json: depth=%d\n", fctx->depth);
+	internal_error("formatting json: depth=%d", fctx->depth);
 	exit(1);
 }
 
 static void fmt_inc_depth(struct format_ctx *fctx)
 {
 	if (fctx->depth >= JSON_NESTING_LIMIT - 1) {
-		printf("INTERNAL ERROR: nesting too deep, limit %d\n",
-				JSON_NESTING_LIMIT);
+		internal_error("nesting too deep, limit %d", JSON_NESTING_LIMIT);
 		exit(1);
 	}
 	fctx->depth++;
@@ -73,7 +72,7 @@ static void fmt_inc_depth(struct format_ctx *fctx)
 static void fmt_dec_depth(struct format_ctx *fctx)
 {
 	if (fctx->depth < 1) {
-		printf("INTERNAL ERROR: nesting below first level\n");
+		internal_error("nesting below first level");
 		exit(1);
 	}
 	fctx->depth--;
@@ -244,7 +243,7 @@ void fmt_print(struct format_ctx *fctx, const char* key, ...)
 		row++;
 	}
 	if (!found) {
-		printf("INTERNAL ERROR: unknown key: %s\n", key);
+		internal_error("unknown key: %s", key);
 		exit(1);
 	}
 
@@ -319,7 +318,7 @@ void fmt_print(struct format_ctx *fctx, const char* key, ...)
 
 		printf("%s", pretty_size_mode(size, unit_mode));
 	} else {
-		printf("INTERNAL ERROR: unknown format %s\n", row->fmt);
+		internal_error("unknown format %s", row->fmt);
 	}
 
 	fmt_end_value(fctx, row);
diff --git a/common/messages.c b/common/messages.c
index bc616849..09716a40 100644
--- a/common/messages.c
+++ b/common/messages.c
@@ -77,6 +77,22 @@ int __btrfs_error_on(int condition, const char *fmt, ...)
 	return 1;
 }
 
+__attribute__ ((format (printf, 1, 2)))
+void internal_error(const char *fmt, ...)
+{
+	va_list vargs;
+
+	va_start(vargs, fmt);
+	fputs("INTERNAL ERROR: ", stderr);
+	vfprintf(stderr, fmt, vargs);
+	va_end(vargs);
+	fputc('\n', stderr);
+
+#ifndef BTRFS_DISABLE_BACKTRACE
+	print_trace();
+#endif
+}
+
 /*
  * Print a message according to the global verbosity level.
  *
diff --git a/common/messages.h b/common/messages.h
index c443bd55..729df140 100644
--- a/common/messages.h
+++ b/common/messages.h
@@ -100,6 +100,9 @@ int __btrfs_warning_on(int condition, const char *fmt, ...);
 __attribute__ ((format (printf, 2, 3)))
 int __btrfs_error_on(int condition, const char *fmt, ...);
 
+__attribute__ ((format (printf, 1, 2)))
+void internal_error(const char *fmt, ...);
+
 /*
  * Level of messages that must be printed by default (in case the verbosity
  * options haven't been set by the user) due to backward compatibility reasons
diff --git a/common/units.c b/common/units.c
index eaeb7e2f..94cfa057 100644
--- a/common/units.c
+++ b/common/units.c
@@ -17,6 +17,7 @@
 #include <stdio.h>
 #include <string.h>
 #include "common/units.h"
+#include "common/messages.h"
 
 /*
  * Note: this function uses a static per-thread buffer. Do not call this
@@ -77,8 +78,7 @@ int pretty_size_snprintf(u64 size, char *str, size_t str_size, unsigned unit_mod
 
 	/* Unknown mode */
 	if (!base) {
-		fprintf(stderr, "INTERNAL ERROR: unknown unit base, mode %u\n",
-				unit_mode);
+		internal_error("unknown unit base, mode %u", unit_mode);
 		assert(0);
 		return -1;
 	}
@@ -134,8 +134,7 @@ int pretty_size_snprintf(u64 size, char *str, size_t str_size, unsigned unit_mod
 
 	if (num_divs >= ARRAY_SIZE(unit_suffix_binary)) {
 		str[0] = '\0';
-		printf("INTERNAL ERROR: unsupported unit suffix, index %d\n",
-				num_divs);
+		internal_error("unsupported unit suffix, index %d", num_divs);
 		assert(0);
 		return -1;
 	}