diff --git a/Header.c b/Header.c
index 929a6e0e25525a5c70264ab8d3f0500ba5720a29..076310582eecb1b5fe7ea115e73aa2133a10ab82 100644
--- a/Header.c
+++ b/Header.c
@@ -37,7 +37,7 @@ typedef struct Header_ {
 #endif
 
 #ifndef Header_forEachColumn
-#define Header_forEachColumn(this_, i_) for (int i_=0; i_ < this->nrColumns; i_++)
+#define Header_forEachColumn(this_, i_) for (int (i_)=0; (i_) < (this_)->nrColumns; ++(i_))
 #endif
 
 Header* Header_new(struct ProcessList_* pl, Settings* settings, int nrColumns) {
diff --git a/Header.h b/Header.h
index 772e25dd13988b056960ec10867c4fd636fff377..700ad354b1a810fe6e00a9a6d5d210af077d0256 100644
--- a/Header.h
+++ b/Header.h
@@ -28,7 +28,7 @@ typedef struct Header_ {
 #endif
 
 #ifndef Header_forEachColumn
-#define Header_forEachColumn(this_, i_) for (int i_=0; i_ < this->nrColumns; i_++)
+#define Header_forEachColumn(this_, i_) for (int (i_)=0; (i_) < (this_)->nrColumns; ++(i_))
 #endif
 
 Header* Header_new(struct ProcessList_* pl, Settings* settings, int nrColumns);