diff --git a/libm65/gran.c b/libm65/gran.c
new file mode 100644
index 000000000..ceeb6da7d
--- /dev/null
+++ b/libm65/gran.c
@@ -0,0 +1,28 @@
+#include <stdlib.h>
+#include <math.h>
+
+/* Generate gaussian random float with mean=0 and std_dev=1 */
+float gran_()
+{
+  float fac,rsq,v1,v2;
+  static float gset;
+  static int iset;
+
+  if(iset){
+    /* Already got one */
+    iset = 0;
+    return gset;
+  }
+  /* Generate two evenly distributed numbers between -1 and +1
+   * that are inside the unit circle
+   */
+  do {
+    v1 = 2.0 * (float)rand() / RAND_MAX - 1;
+    v2 = 2.0 * (float)rand() / RAND_MAX - 1;
+    rsq = v1*v1 + v2*v2;
+  } while(rsq >= 1.0 || rsq == 0.0);
+  fac = sqrt(-2.0*log(rsq)/rsq);
+  gset = v1*fac;
+  iset++;
+  return v2*fac;
+}