diff --git a/dfs.h b/dfs.h
index 43747ca5f..5213309d6 100644
--- a/dfs.h
+++ b/dfs.h
@@ -17,8 +17,8 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef DFS_H_INCLUDED
-#define DFS_H_INCLUDED
+#ifndef OPM_DFS_HEADER_INCLUDED
+#define OPM_DFS_HEADER_INCLUDED
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/flow_bc.h b/flow_bc.h
index 30430a036..6da3e81c0 100644
--- a/flow_bc.h
+++ b/flow_bc.h
@@ -17,8 +17,8 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef FLOW_BC_H_INCLUDED
-#define FLOW_BC_H_INCLUDED
+#ifndef OPM_FLOW_BC_HEADER_INCLUDED
+#define OPM_FLOW_BC_HEADER_INCLUDED
 
 #include <stddef.h>
 
@@ -46,4 +46,4 @@ deallocate_flowbc(flowbc_t *fbc);
 }
 #endif
 
-#endif  /* FLOW_BC_H_INCLUDED */
+#endif  /* OPM_FLOW_BC_HEADER_INCLUDED */
diff --git a/mimetic.h b/mimetic.h
index 1b73aa1cc..659cbb286 100644
--- a/mimetic.h
+++ b/mimetic.h
@@ -17,8 +17,8 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef MIMETIC_H_INCLUDED
-#define MIMETIC_H_INCLUDED
+#ifndef OPM_MIMETIC_HEADER_INCLUDED
+#define OPM_MIMETIC_HEADER_INCLUDED
 
 #ifdef __cplusplus
 extern "C" {
@@ -85,4 +85,4 @@ void mim_ip_simple_all(int ncells, int d, int max_ncf, int *ncf,
 }
 #endif
 
-#endif /* MIMETIC_H_INCLUDED */
+#endif /* OPM_MIMETIC_HEADER_INCLUDED */
diff --git a/partition.h b/partition.h
index 7a8115293..61336e663 100644
--- a/partition.h
+++ b/partition.h
@@ -17,8 +17,8 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef PARTITION_H_INCLUDED
-#define PARTITION_H_INCLUDED
+#ifndef OPM_PARTITION_HEADER_INCLUDED
+#define OPM_PARTITION_HEADER_INCLUDED
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/sparse_sys.h b/sparse_sys.h
index e9b9d75de..b53491e0b 100644
--- a/sparse_sys.h
+++ b/sparse_sys.h
@@ -17,8 +17,8 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef SPARSE_SYS_H_INCLUDED
-#define SPARSE_SYS_H_INCLUDED
+#ifndef OPM_SPARSE_SYS_HEADER_INCLUDED
+#define OPM_SPARSE_SYS_HEADER_INCLUDED
 
 #include <stddef.h>
 
@@ -76,4 +76,4 @@ csrmatrix_zero(struct CSRMatrix *A);
 }
 #endif
 
-#endif  /* SPARSE_SYS_H_INCLUDED */
+#endif  /* OPM_SPARSE_SYS_HEADER_INCLUDED */
diff --git a/well.h b/well.h
index f2e3ceeae..d4d0dae90 100644
--- a/well.h
+++ b/well.h
@@ -17,8 +17,8 @@
   along with OPM.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#ifndef WELL_H_INCLUDED
-#define WELL_H_INCLUDED
+#ifndef OPM_WELL_HEADER_INCLUDED
+#define OPM_WELL_HEADER_INCLUDED
 
 #ifdef __cplusplus
 extern "C" {
@@ -54,4 +54,4 @@ derive_cell_wells(int nc, well_t *W, int *cwpos, int *cwells);
 }
 #endif
 
-#endif /* WELL_H_INCLUDED */
+#endif /* OPM_WELL_HEADER_INCLUDED */