diff --git a/utest.h b/utest.h
index d932e1b..a981162 100644
--- a/utest.h
+++ b/utest.h
@@ -204,7 +204,7 @@
 #define UTEST_NULL 0
 #endif
 
-#ifndef UTEST_DETECT_USE_COLOUR
+#if !defined(UTEST_DETECT_USE_COLOUR) && !defined(__EMSCRIPTEN__)
 #define UTEST_COLOUR_OUTPUT() true
 #else
 #ifdef _MSC_VER
@@ -321,17 +321,17 @@
 #define UTEST_SNPRINTF(...) snprintf(__VA_ARGS__)
 #endif
 
-#define UTEST_PRINTF(...)                                                      \
-  if (utest_state.output) {                                                    \
-    size_t new_bytes = UTEST_SNPRINTF(0, 0, __VA_ARGS__);                      \
-    if (new_bytes > 0) {                                                       \
-      utest_state.output_buffer = (char*)realloc(utest_state.output_buffer,    \
-          utest_state.buffer_size+new_bytes);                                  \
-      utest_state.buffer_size += UTEST_SNPRINTF(utest_state.output_buffer      \
-          + utest_state.buffer_size - 1,                                       \
-          utest_state.buffer_size+new_bytes, __VA_ARGS__);                     \
-    }                                                                          \
-  }                                                                            \
+#define UTEST_PRINTF(...)                                                         \
+  if (utest_state.output) {                                                       \
+    size_t new_bytes = UTEST_SNPRINTF(0, 0, __VA_ARGS__);                         \
+    if (new_bytes > 0) {                                                          \
+      utest_state.output_buffer = (char*)utest_realloc(utest_state.output_buffer, \
+          utest_state.buffer_size+new_bytes);                                     \
+      utest_state.buffer_size += UTEST_SNPRINTF(utest_state.output_buffer         \
+          + utest_state.buffer_size - 1,                                          \
+          utest_state.buffer_size+new_bytes, __VA_ARGS__);                        \
+    }                                                                             \
+  }                                                                               \
   printf(__VA_ARGS__)
 
 #ifdef __clang__