diff --git a/pkgs/pkgs-lib/formats/java-properties/default.nix b/pkgs/pkgs-lib/formats/java-properties/default.nix
index 6ac56bff4bf6..d3a4761f0f80 100644
--- a/pkgs/pkgs-lib/formats/java-properties/default.nix
+++ b/pkgs/pkgs-lib/formats/java-properties/default.nix
@@ -1,6 +1,10 @@
 { lib, pkgs }:
+let
+  inherit (lib) types;
+  inherit (types) attrsOf oneOf coercedTo str bool int float package;
+in
 {
-  javaProperties = { comment ? "Generated with Nix" }: {
+  javaProperties = { comment ? "Generated with Nix", boolToString ? lib.boolToString }: {
 
     # Design note:
     # A nested representation of inevitably leads to bad UX:
@@ -25,7 +29,21 @@
     # We _can_ choose to support hierarchical config files
     # via nested attrsets, but the module author should
     # make sure that problem (2) does not occur.
-    type = lib.types.attrsOf lib.types.str;
+    type = let
+      elemType =
+        oneOf ([
+          # `package` isn't generalized to `path` because path values
+          # are ambiguous. Are they host path strings (toString /foo/bar)
+          # or should they be added to the store? ("${/foo/bar}")
+          # The user must decide.
+          (coercedTo package toString str)
+
+          (coercedTo bool boolToString str)
+          (coercedTo int toString str)
+          (coercedTo float toString str)
+        ])
+        // { description = "string, package, bool, int or float"; };
+      in attrsOf elemType;
 
     generate = name: value:
       pkgs.runCommandLocal name
diff --git a/pkgs/pkgs-lib/formats/java-properties/test/default.nix b/pkgs/pkgs-lib/formats/java-properties/test/default.nix
index 4b3845c10296..c45cfd90031f 100644
--- a/pkgs/pkgs-lib/formats/java-properties/test/default.nix
+++ b/pkgs/pkgs-lib/formats/java-properties/test/default.nix
@@ -5,6 +5,12 @@
 , lib
 , stdenv
 }:
+
+# This test primarily tests correct escaping.
+# See also testJavaProperties in
+# pkgs/pkgs-lib/tests/formats.nix, which tests
+# type coercions and is a bit easier to read.
+
 let
   inherit (lib) concatStrings attrValues mapAttrs;
 
diff --git a/pkgs/pkgs-lib/tests/formats.nix b/pkgs/pkgs-lib/tests/formats.nix
index 25327acfe7a4..86ef4c6d2691 100644
--- a/pkgs/pkgs-lib/tests/formats.nix
+++ b/pkgs/pkgs-lib/tests/formats.nix
@@ -176,11 +176,21 @@ in runBuildTests {
     '';
   };
 
-  # See also java-properties/default.nix for more complete tests
+  # This test is responsible for
+  #   1. testing type coercions
+  #   2. providing a more readable example test
+  # Whereas java-properties/default.nix tests the low level escaping, etc.
   testJavaProperties = {
     drv = evalFormat formats.javaProperties {} {
+      floaty = 3.1415;
+      tautologies = true;
+      contradictions = false;
       foo = "bar";
-      "1" = "2";
+      # # Disallowed at eval time, because it's ambiguous:
+      # # add to store or convert to string?
+      # root = /root;
+      "1" = 2;
+      package = pkgs.hello;
       "ütf 8" = "dûh";
       # NB: Some editors (vscode) show this _whole_ line in right-to-left order
       "الجبر" = "أكثر من مجرد أرقام";
@@ -189,7 +199,11 @@ in runBuildTests {
       # Generated with Nix
 
       1 = 2
+      contradictions = false
+      floaty = 3.141500
       foo = bar
+      package = ${pkgs.hello}
+      tautologies = true
       \u00fctf\ 8 = d\u00fbh
       \u0627\u0644\u062c\u0628\u0631 = \u0623\u0643\u062b\u0631 \u0645\u0646 \u0645\u062c\u0631\u062f \u0623\u0631\u0642\u0627\u0645
     '';