diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 81b0a3b48e76..4e99e1fac86c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2016-12-12  Uros Bizjak  <ubizjak@gmail.com>
+
+	PR target/78738
+	* config/i386/i386.h (X87_ENABLE_ARITH): Also enable for
+	flag_unsafe_math_optimizations.
+	(X87_ENABLE_FLOAT): Ditto.
+
 2016-12-12  Marek Polacek  <polacek@redhat.com>
 
 	PR middle-end/78716
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 8bc31f9187d5..4d96a4525fb7 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -693,13 +693,16 @@ extern const char *host_detect_local_cpu (int argc, const char **argv);
 /* Whether to allow x87 floating-point arithmetic on MODE (one of
    SFmode, DFmode and XFmode) in the current excess precision
    configuration.  */
-#define X87_ENABLE_ARITH(MODE) \
-  (flag_excess_precision == EXCESS_PRECISION_FAST || (MODE) == XFmode)
+#define X87_ENABLE_ARITH(MODE)				\
+  (flag_unsafe_math_optimizations			\
+   || flag_excess_precision == EXCESS_PRECISION_FAST	\
+   || (MODE) == XFmode)
 
 /* Likewise, whether to allow direct conversions from integer mode
    IMODE (HImode, SImode or DImode) to MODE.  */
 #define X87_ENABLE_FLOAT(MODE, IMODE)			\
-  (flag_excess_precision == EXCESS_PRECISION_FAST	\
+  (flag_unsafe_math_optimizations			\
+   || flag_excess_precision == EXCESS_PRECISION_FAST	\
    || (MODE) == XFmode					\
    || ((MODE) == DFmode && (IMODE) == SImode)		\
    || (IMODE) == HImode)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 35db8198c28a..510586915627 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-12-12  Uros Bizjak  <ubizjak@gmail.com>
+
+	PR target/78738
+	* gcc.target/i386/pr78738.c: New test.
+
 2016-12-12  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* lib/target-supports.exp
diff --git a/gcc/testsuite/gcc.target/i386/pr78738.c b/gcc/testsuite/gcc.target/i386/pr78738.c
new file mode 100644
index 000000000000..d2a2a62990b1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr78738.c
@@ -0,0 +1,10 @@
+/* PR middle-end/78738 */
+/* { dg-do compile } */
+/* { dg-options "-O -std=c99 -ffast-math -mfpmath=387" } */
+
+double round (double);
+
+int foo (double a)
+{
+  return round (a);
+}