diff --git a/include/mbedtls/base64.h b/include/mbedtls/base64.h
index 635be71..e82c270 100644
--- a/include/mbedtls/base64.h
+++ b/include/mbedtls/base64.h
@@ -87,6 +87,35 @@
 
 #endif /* MBEDTLS_SELF_TEST */
 
+#if defined(MBEDTLS_TEST_HOOKS)
+
+/** Given a value in the range 0..63, return the corresponding Base64 digit.
+ *
+ * The implementation assumes that letters are consecutive (e.g. ASCII
+ * but not EBCDIC).
+ *
+ * \param value     A value in the range 0..63.
+ *
+ * \return          A base64 digit converted from \p value.
+ */
+unsigned char mbedtls_ct_base64_enc_char(unsigned char value);
+
+/** Given a Base64 digit, return its value.
+ *
+ * If c is not a Base64 digit ('A'..'Z', 'a'..'z', '0'..'9', '+' or '/'),
+ * return -1.
+ *
+ * The implementation assumes that letters are consecutive (e.g. ASCII
+ * but not EBCDIC).
+ *
+ * \param c     A base64 digit.
+ *
+ * \return      The value of the base64 digit \p c.
+ */
+signed char mbedtls_ct_base64_dec_value(unsigned char c);
+
+#endif /* MBEDTLS_TEST_HOOKS */
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/library/base64.c b/library/base64.c
index 3eb9e7c..3f13fda 100644
--- a/library/base64.c
+++ b/library/base64.c
@@ -33,6 +33,39 @@
 #include "mbedtls/platform.h"
 #endif /* MBEDTLS_SELF_TEST */
 
+MBEDTLS_STATIC_TESTABLE
+unsigned char mbedtls_ct_base64_enc_char(unsigned char value)
+{
+    unsigned char digit = 0;
+    /* For each range of values, if value is in that range, mask digit with
+     * the corresponding value. Since value can only be in a single range,
+     * only at most one masking will change digit. */
+    digit |= mbedtls_ct_uchar_mask_of_range(0, 25, value) & ('A' + value);
+    digit |= mbedtls_ct_uchar_mask_of_range(26, 51, value) & ('a' + value - 26);
+    digit |= mbedtls_ct_uchar_mask_of_range(52, 61, value) & ('0' + value - 52);
+    digit |= mbedtls_ct_uchar_mask_of_range(62, 62, value) & '+';
+    digit |= mbedtls_ct_uchar_mask_of_range(63, 63, value) & '/';
+    return digit;
+}
+
+MBEDTLS_STATIC_TESTABLE
+signed char mbedtls_ct_base64_dec_value(unsigned char c)
+{
+    unsigned char val = 0;
+    /* For each range of digits, if c is in that range, mask val with
+     * the corresponding value. Since c can only be in a single range,
+     * only at most one masking will change val. Set val to one plus
+     * the desired value so that it stays 0 if c is in none of the ranges. */
+    val |= mbedtls_ct_uchar_mask_of_range('A', 'Z', c) & (c - 'A' +  0 + 1);
+    val |= mbedtls_ct_uchar_mask_of_range('a', 'z', c) & (c - 'a' + 26 + 1);
+    val |= mbedtls_ct_uchar_mask_of_range('0', '9', c) & (c - '0' + 52 + 1);
+    val |= mbedtls_ct_uchar_mask_of_range('+', '+', c) & (c - '+' + 62 + 1);
+    val |= mbedtls_ct_uchar_mask_of_range('/', '/', c) & (c - '/' + 63 + 1);
+    /* At this point, val is 0 if c is an invalid digit and v+1 if c is
+     * a digit with the value v. */
+    return val - 1;
+}
+
 /*
  * Encode a buffer into base64 format
  */
diff --git a/library/constant_time.c b/library/constant_time.c
index c823b78..1f6c2ca 100644
--- a/library/constant_time.c
+++ b/library/constant_time.c
@@ -212,7 +212,6 @@
  *
  * Constant flow with respect to c.
  */
-MBEDTLS_STATIC_TESTABLE
 unsigned char mbedtls_ct_uchar_mask_of_range(unsigned char low,
                                              unsigned char high,
                                              unsigned char c)
@@ -344,41 +343,6 @@
 
 #endif /* MBEDTLS_BIGNUM_C */
 
-#if defined(MBEDTLS_BASE64_C)
-
-unsigned char mbedtls_ct_base64_enc_char(unsigned char value)
-{
-    unsigned char digit = 0;
-    /* For each range of values, if value is in that range, mask digit with
-     * the corresponding value. Since value can only be in a single range,
-     * only at most one masking will change digit. */
-    digit |= mbedtls_ct_uchar_mask_of_range(0, 25, value) & ('A' + value);
-    digit |= mbedtls_ct_uchar_mask_of_range(26, 51, value) & ('a' + value - 26);
-    digit |= mbedtls_ct_uchar_mask_of_range(52, 61, value) & ('0' + value - 52);
-    digit |= mbedtls_ct_uchar_mask_of_range(62, 62, value) & '+';
-    digit |= mbedtls_ct_uchar_mask_of_range(63, 63, value) & '/';
-    return digit;
-}
-
-signed char mbedtls_ct_base64_dec_value(unsigned char c)
-{
-    unsigned char val = 0;
-    /* For each range of digits, if c is in that range, mask val with
-     * the corresponding value. Since c can only be in a single range,
-     * only at most one masking will change val. Set val to one plus
-     * the desired value so that it stays 0 if c is in none of the ranges. */
-    val |= mbedtls_ct_uchar_mask_of_range('A', 'Z', c) & (c - 'A' +  0 + 1);
-    val |= mbedtls_ct_uchar_mask_of_range('a', 'z', c) & (c - 'a' + 26 + 1);
-    val |= mbedtls_ct_uchar_mask_of_range('0', '9', c) & (c - '0' + 52 + 1);
-    val |= mbedtls_ct_uchar_mask_of_range('+', '+', c) & (c - '+' + 62 + 1);
-    val |= mbedtls_ct_uchar_mask_of_range('/', '/', c) & (c - '/' + 63 + 1);
-    /* At this point, val is 0 if c is an invalid digit and v+1 if c is
-     * a digit with the value v. */
-    return val - 1;
-}
-
-#endif /* MBEDTLS_BASE64_C */
-
 #if defined(MBEDTLS_PKCS1_V15) && defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_RSA_ALT)
 
 /** Shift some data towards the left inside a buffer.
diff --git a/library/constant_time_internal.h b/library/constant_time_internal.h
index c4a32c7..4ca3925 100644
--- a/library/constant_time_internal.h
+++ b/library/constant_time_internal.h
@@ -185,35 +185,6 @@
 
 #endif /* MBEDTLS_BIGNUM_C */
 
-#if defined(MBEDTLS_BASE64_C)
-
-/** Given a value in the range 0..63, return the corresponding Base64 digit.
- *
- * The implementation assumes that letters are consecutive (e.g. ASCII
- * but not EBCDIC).
- *
- * \param value     A value in the range 0..63.
- *
- * \return          A base64 digit converted from \p value.
- */
-unsigned char mbedtls_ct_base64_enc_char(unsigned char value);
-
-/** Given a Base64 digit, return its value.
- *
- * If c is not a Base64 digit ('A'..'Z', 'a'..'z', '0'..'9', '+' or '/'),
- * return -1.
- *
- * The implementation assumes that letters are consecutive (e.g. ASCII
- * but not EBCDIC).
- *
- * \param c     A base64 digit.
- *
- * \return      The value of the base64 digit \p c.
- */
-signed char mbedtls_ct_base64_dec_value(unsigned char c);
-
-#endif /* MBEDTLS_BASE64_C */
-
 #if defined(MBEDTLS_SSL_SOME_SUITES_USE_MAC)
 
 /** Conditional memcpy without branches.
@@ -360,4 +331,16 @@
 
 #endif /* MBEDTLS_PKCS1_V15 && MBEDTLS_RSA_C && ! MBEDTLS_RSA_ALT */
 
+#if defined(MBEDTLS_BASE64_C)
+
+/* Return 0xff if low <= c <= high, 0 otherwise.
+ *
+ * Constant flow with respect to c.
+ */
+unsigned char mbedtls_ct_uchar_mask_of_range(unsigned char low,
+                                             unsigned char high,
+                                             unsigned char c);
+
+#endif /* MBEDTLS_BASE64_C */
+
 #endif /* MBEDTLS_CONSTANT_TIME_INTERNAL_H */