diff --git a/man7/feature_test_macros.7 b/man7/feature_test_macros.7
index 1dc3ff639..545abac0b 100644
--- a/man7/feature_test_macros.7
+++ b/man7/feature_test_macros.7
@@ -187,7 +187,7 @@ This macro is also implicitly defined if
 is defined with a value of 500 or more.
 .TP
 .B _ISOC99_SOURCE
-Exposes C 99 extensions to ISO C (1990).
+Exposes C99 extensions to ISO C (1990).
 This macro is recognized since glibc 2.1.3;
 earlier glibc 2.1.x versions recognized an equivalent macro named
 .B _ISOC9X_SOURCE
diff --git a/man7/unicode.7 b/man7/unicode.7
index ae13e0ab6..73984560e 100644
--- a/man7/unicode.7
+++ b/man7/unicode.7
@@ -185,7 +185,7 @@ by the C library as
 code values (in all locales), a convention that is signaled by the GNU
 C library to applications by defining the constant
 .B __STDC_ISO_10646__
-as specified in the ISO C 99 standard.
+as specified in the ISO C99 standard.
 
 UCS/Unicode can be used just like ASCII in input/output streams,
 terminal communication, plaintext files, filenames, and environment
@@ -259,7 +259,7 @@ A good reference book about the C programming language.
 The fourth
 edition covers the 1994 Amendment 1 to the ISO C 90 standard, which
 adds a large number of new C library functions for handling wide and
-multi-byte character encodings, but it does not yet cover ISO C 99,
+multi-byte character encodings, but it does not yet cover ISO C99,
 which improved wide and multi-byte character support even further.
 .TP
 *