diff --git a/src/m_pd.h b/src/m_pd.h
index c658fa5..a3a506c 100644
--- a/src/m_pd.h
+++ b/src/m_pd.h
@@ -8,6 +8,8 @@
 extern "C" {
 #endif
 
+extern void error(const char* fmt, ...);
+
 #define PD_MAJOR_VERSION 0
 #define PD_MINOR_VERSION 54
 #define PD_BUGFIX_VERSION 1