diff --git a/builtin.c b/builtin.c
index 105290ca..c9b1868f 100644
--- a/builtin.c
+++ b/builtin.c
@@ -1155,6 +1155,12 @@ static const char* const jq_builtins[] = {
   "         exp, _repeat;"
   "     try _repeat catch if .==\"break\" then empty else . end;",
   "def inputs: repeat(_input);",
+  // # like ruby's downcase - only characters A to Z are affected
+  "def ascii_downcase:"
+  "  explode | map( if 65 <= . and . <= 90 then . + 32  else . end) | implode;",
+  // # like ruby's upcase - only characters a to z are affected
+  "def ascii_upcase:"
+  "  explode | map( if 97 <= . and . <= 122 then . - 32  else . end) | implode;",
 };
 #undef LIBM_DD
 
diff --git a/docs/content/3.manual/manual.yml b/docs/content/3.manual/manual.yml
index 5e4467c4..cfd87c24 100644
--- a/docs/content/3.manual/manual.yml
+++ b/docs/content/3.manual/manual.yml
@@ -1312,6 +1312,18 @@ sections:
             input: '["a","b,c,d","e"]'
             output: ['"a, b,c,d, e"']
 
+
+      - title: "`ascii_downcase`, `ascii_upcase`"
+        body: |
+
+          Emit a copy of the input string with its alphabetic characters (a-z and A-Z) 
+          converted to the specified case.
+
+        example:
+          - program: 'ascii_upcase'
+            input: '"useful but not for é"'
+            output: '"USEFUL BUT NOT FOR é"'
+
       - title: "`while(cond; update)`"
         body: |
 
diff --git a/tests/all.test b/tests/all.test
index e91810f0..f632e43e 100644
--- a/tests/all.test
+++ b/tests/all.test
@@ -1107,3 +1107,7 @@ flatten(2)
 transpose
 [[1], [2,3]]
 [[1,2],[null,3]]
+
+ascii_upcase
+"useful but not for é"
+"USEFUL BUT NOT FOR é"