diff --git a/src/plugindata.h b/src/plugindata.h
index 54da4b522..db84254b7 100644
--- a/src/plugindata.h
+++ b/src/plugindata.h
@@ -30,8 +30,8 @@
  * when making changes (see 'Keeping the plugin ABI stable' in the HACKING file). */
 
 
-#ifndef PLUGINDATA_H
-#define PLUGINDATA_H
+#ifndef GEANY_PLUGINDATA_H
+#define GEANY_PLUGINDATA_H
 
 /* Compatibility for sharing macros between API and core.
  * First include geany.h, then plugindata.h, then other API headers. */
diff --git a/src/pluginprivate.h b/src/pluginprivate.h
index e705d834d..f88bf1f19 100644
--- a/src/pluginprivate.h
+++ b/src/pluginprivate.h
@@ -21,8 +21,8 @@
  */
 
 
-#ifndef PLUGINPRIVATE_H
-#define PLUGINPRIVATE_H
+#ifndef GEANY_PLUGINPRIVATE_H
+#define GEANY_PLUGINPRIVATE_H
 
 #include "plugindata.h"
 #include "ui_utils.h"	/* GeanyAutoSeparator */
@@ -62,4 +62,4 @@ GeanyPluginPrivate;
 typedef GeanyPluginPrivate Plugin;	/* shorter alias */
 
 
-#endif /* PLUGINPRIVATE_H */
+#endif /* GEANY_PLUGINPRIVATE_H */
diff --git a/src/plugins.h b/src/plugins.h
index fb49d2b23..a7d003123 100644
--- a/src/plugins.h
+++ b/src/plugins.h
@@ -21,8 +21,8 @@
  */
 
 
-#ifndef PLUGINS_H
-#define PLUGINS_H
+#ifndef GEANY_PLUGINS_H
+#define GEANY_PLUGINS_H
 
 #ifdef HAVE_PLUGINS
 
diff --git a/src/pluginutils.h b/src/pluginutils.h
index c02094d17..5051f7a57 100644
--- a/src/pluginutils.h
+++ b/src/pluginutils.h
@@ -21,8 +21,8 @@
  */
 
 
-#ifndef PLUGINUTILS_H
-#define PLUGINUTILS_H
+#ifndef GEANY_PLUGINUTILS_H
+#define GEANY_PLUGINUTILS_H
 
 #ifdef HAVE_PLUGINS
 
@@ -55,4 +55,4 @@ struct GeanyKeyGroup *plugin_set_key_group(struct GeanyPlugin *plugin,
 void plugin_show_configure(struct GeanyPlugin *plugin);
 
 #endif /* HAVE_PLUGINS */
-#endif /* PLUGINUTILS_H */
+#endif /* GEANY_PLUGINUTILS_H */
diff --git a/src/prefix.h b/src/prefix.h
index e11b407c3..1c25f7b91 100644
--- a/src/prefix.h
+++ b/src/prefix.h
@@ -14,8 +14,8 @@
  * to br_*", try renaming prefix.c to prefix.cpp
  */
 
-#ifndef _PREFIX_H_
-#define _PREFIX_H_
+#ifndef GEANY_PREFIX_H
+#define GEANY_PREFIX_H
 
 
 /*
@@ -93,4 +93,4 @@ char *br_prepend_prefix	(void *symbol, char *path);
 
 #endif /* ENABLE_BINRELOC */
 
-#endif /* _PREFIX_H_ */
+#endif /* GEANY_PREFIX_H */