diff --git a/build.sh b/build.sh
index d650d52..ba5eb65 100755
--- a/build.sh
+++ b/build.sh
@@ -6,6 +6,13 @@
 source util.sh
 cd build
 
+# Number of processor cores
+if [[ $(uname) == "OpenBSD" ]]; then
+  cores=$(sysctl -n hw.ncpu)
+else
+  cores=$(nproc)
+fi
+
 echo "$TAG Compiling gcc (usually 10-20 minutes)..."
 run_quietly giteapc-build.log \
-make -j$(nproc) all-gcc all-target-libgcc
+make -j"$cores" all-gcc all-target-libgcc