diff --git a/pkgs/racket-test-core/tests/racket/number.rktl b/pkgs/racket-test-core/tests/racket/number.rktl
index d6dd69800d..968562d2fd 100644
--- a/pkgs/racket-test-core/tests/racket/number.rktl
+++ b/pkgs/racket-test-core/tests/racket/number.rktl
@@ -1607,6 +1607,9 @@
 (test +inf.0 magnitude 0.0+inf.0i)
 (test +nan.0 magnitude +nan.0+inf.0i)
 (test +nan.0 magnitude +inf.0+nan.0i)
+(test +inf.f magnitude 3.0f0-inf.fi)
+(test +nan.f magnitude 3.0f0+nan.fi)
+(test 3.0f0 magnitude 3.0f0+0.0f0i)
 
 (test 0 angle 1)
 (test 0 angle 1.0)
diff --git a/racket/src/racket/src/number.c b/racket/src/racket/src/number.c
index 16b4eeee5d..bb20444a58 100644
--- a/racket/src/racket/src/number.c
+++ b/racket/src/racket/src/number.c
@@ -3804,6 +3804,21 @@ static Scheme_Object *magnitude(int argc, Scheme_Object *argv[])
       a[0] = i;
       return scheme_exact_to_inexact(1, a);
     }
+#ifdef MZ_USE_SINGLE_FLOATS
+    if (SCHEME_FLTP(i)) {
+      float f;
+      f = SCHEME_FLT_VAL(i);
+      if (MZ_IS_POS_INFINITY((double) f)) {
+        if (SCHEME_FLTP(r)) { /* `r` is either a single-precision float or exact 0 */
+          f = SCHEME_FLT_VAL(r);
+          if (MZ_IS_NAN((double) f)) {
+            return scheme_single_nan_object;
+          }
+          return scheme_single_inf_object;
+        }
+      }
+    }
+#endif
     if (SCHEME_FLOATP(i)) {
       double d;
       d = SCHEME_FLOAT_VAL(i);