diff --git a/opm/core/pressure/FlowBCManager.cpp b/opm/core/pressure/FlowBCManager.cpp
index 81675d710..85549e8c7 100644
--- a/opm/core/pressure/FlowBCManager.cpp
+++ b/opm/core/pressure/FlowBCManager.cpp
@@ -197,7 +197,7 @@ namespace Opm
 	    // min/max i/j/k (depending on side).
 	    const int correct_ijk = (side % 2) ? grid.cartdims[side/2] : 0;
 	    for (int c = 0; c < grid.number_of_cells; ++c) {
-		int ijk[3] = { -1 };
+		int ijk[3] = { -1, -1, -1 };
 		cartCoord(grid.global_cell[c], grid.cartdims, ijk);
 		if (ijk[side/2] != correct_ijk) {
 		    continue;