diff --git a/library/constant_time.c b/library/constant_time.c
index b513c6a..6d53134 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -273,3 +273,19 @@
 }
 
 #endif /* MBEDTLS_BIGNUM_C */
+
+/** Choose between two integer values, without branches.
+ *
+ * This is equivalent to `cond ? if1 : if0`, but is likely to be compiled
+ * to code using bitwise operation rather than a branch.
+ *
+ * \param cond      Condition to test.
+ * \param if1       Value to use if \p cond is nonzero.
+ * \param if0       Value to use if \p cond is zero.
+ * \return          \c if1 if \p cond is nonzero, otherwise \c if0.
+ */
+unsigned mbedtls_cf_uint_if( unsigned cond, unsigned if1, unsigned if0 )
+{
+    unsigned mask = mbedtls_cf_uint_mask( cond );
+    return( ( mask & if1 ) | (~mask & if0 ) );
+}
diff --git a/library/constant_time.h b/library/constant_time.h
index 3c18b4e..973e856 100644
--- a/library/constant_time.h
+++ b/library/constant_time.h
@@ -52,3 +52,6 @@
                                  const mbedtls_mpi_uint y );
 
 #endif /* MBEDTLS_BIGNUM_C */
+
+unsigned mbedtls_cf_uint_if( unsigned cond, unsigned if1, unsigned if0 );
+
diff --git a/library/rsa.c b/library/rsa.c
index 21d6d12..a75906a 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -1458,22 +1458,6 @@
 #endif /* MBEDTLS_PKCS1_V21 */
 
 #if defined(MBEDTLS_PKCS1_V15)
-/** Choose between two integer values, without branches.
- *
- * This is equivalent to `cond ? if1 : if0`, but is likely to be compiled
- * to code using bitwise operation rather than a branch.
- *
- * \param cond      Condition to test.
- * \param if1       Value to use if \p cond is nonzero.
- * \param if0       Value to use if \p cond is zero.
- * \return          \c if1 if \p cond is nonzero, otherwise \c if0.
- */
-static unsigned mbedtls_cf_uint_if( unsigned cond, unsigned if1, unsigned if0 )
-{
-    unsigned mask = mbedtls_cf_uint_mask( cond );
-    return( ( mask & if1 ) | (~mask & if0 ) );
-}
-
 /** Shift some data towards the left inside a buffer without leaking
  * the length of the data through side channels.
  *