diff --git a/Doc/c-api/decimal.rst b/Doc/c-api/decimal.rst
index f530571ebae577..94cc4a7b845791 100644
--- a/Doc/c-api/decimal.rst
+++ b/Doc/c-api/decimal.rst
@@ -16,7 +16,7 @@ Initialize
 Typically, a C extension module that uses the decimal API will do these
 steps in its init function:
 
-.. code-block::
+.. code-block:: c
 
     #include "pydecimal.h"
 
@@ -88,7 +88,7 @@ Data structures
 
 The conversion functions use the following status codes and data structures:
 
-.. code-block::
+.. code-block:: c
 
    /* status cases for getting a triple */
    enum mpd_triple_class {
@@ -126,7 +126,7 @@ Functions
    For simplicity, the usage of the function and all special cases are
    explained in code form and comments:
 
-.. code-block::
+.. code-block:: c
 
     triple = PyDec_AsUint128Triple(dec);
     switch (triple.tag) {