diff --git a/check/fixes.frm b/check/fixes.frm
index 3ad37168..94c7198c 100644
--- a/check/fixes.frm
+++ b/check/fixes.frm
@@ -2619,6 +2619,36 @@ Print;
 assert succeeded?
 assert result("test") =~ expr("prf(16*x + 16*y - 8*z,z)*pf(8) + prf(8,1)*pf( - 8*z + 16*y + 16*x)")
 *--#] Issue313 :
+*--#[ Issue315 :
+#-
+Symbol x;
+Local test = 22400/27/(2+x)/(4+x)*replace_(x,134);
+Print;
+.end
+assert succeeded?
+assert result("test") =~ expr("1400/31671")
+*--#] Issue315 :
+*--#[ Issue316 :
+#-
+Symbol a,b,c,d;
+Local test1 = 1/(2*a)/(2*a)*replace_(a,b);
+Local test2 = 1/(2*a)/(3*c)*replace_(a,b,c,d);
+Local test3 = 1/(1+a)/(1+c)/(1+a+c)*replace_(a,b,c,d);
+Local test4 = 1/(1+a/(1+b))*replace_(a,b);
+Local test5 = 1/(2*a/(2*b))*replace_(a,b);
+Local test6 = exp_(2*a*exp_(2*b,2),2);
+Local test7 = exp_(2*a,1+c)*replace_(a,b,c,d);
+Print;
+.end
+assert succeeded?
+assert result("test1") =~ expr("1/4*b^-2")
+assert result("test2") =~ expr("1/6*b^-1*d^-1")
+assert result("test3") =~ expr("1/(1 + b)/(1 + d)/(1 + d + b)")
+assert result("test4") =~ expr("1/(1 + 1/(1 + b)*b)")
+assert result("test5") =~ expr("1")
+assert result("test6") =~ expr("64*a^2*b^4")
+assert result("test7") =~ expr("(2*b)^(1 + d)")
+*--#] Issue316 :
 *--#[ Issue324 :
 * Wrong implicit symbol declaration in "autodeclare index"
 autodeclare index randomIndex=n;
diff --git a/sources/normal.c b/sources/normal.c
index d114c18e..d4bfeb15 100644
--- a/sources/normal.c
+++ b/sources/normal.c
@@ -2699,7 +2699,11 @@ TryAgain:;
 		for ( i = 0; i < nden; i++ ) {
 			t = pden[i];
 			if ( ( t[2] & DIRTYFLAG ) == 0 ) continue;
-			t[2] = 0;
+			/* Before marking clean, we have to check the denominator argument is
+			 * itself clean and does not contain subexpressions. */
+			if ( ( t[FUNHEAD] < 0 || t[FUNHEAD+1] == 0 ) && ! TestFunFlag(BHEAD t) ) {
+				t[2] = 0;
+			}
 			if ( t[FUNHEAD] == -SYMBOL ) {
 				WORD change;
 				t += FUNHEAD+1;
@@ -5311,7 +5315,13 @@ Nexti:;
 int TestFunFlag(PHEAD WORD *tfun)
 {
 	WORD *t, *tstop, *r, *rstop, *m, *mstop;
-	if ( functions[*tfun-FUNCTION].spec <= 0 ) return(0);
+	/* DENOMINATOR and EXPONENT functions have spec <= 0, but may have
+	 * subexpression arguments to search for. */
+	if ( *tfun != DENOMINATOR && *tfun != EXPONENT
+		&& functions[*tfun-FUNCTION].spec <= 0 ) {
+
+		return(0);
+	}
 	tstop = tfun + tfun[1];
 	t = tfun + FUNHEAD;
 	while ( t < tstop ) {