diff --git a/config/nimdoc.cfg b/config/nimdoc.cfg
index a2860af142..6fca53545c 100644
--- a/config/nimdoc.cfg
+++ b/config/nimdoc.cfg
@@ -297,6 +297,23 @@ input#searchInput {
   width: 80%;
 }
 
+/*
+ * Some custom formatting for input forms.
+ * This also fixes input form colors on Firefox with a dark system theme on Linux.
+ */
+input {
+  -moz-appearance: none;
+  color: #333;
+  background-color: #f8f8f8;
+  border: 1px solid #aaa;
+  font-family: "Lato", "Helvetica Neue", "HelveticaNeue", Helvetica, Arial, sans-serif;
+  font-size: 0.9em;
+  padding: 6px;
+}
+input:focus {
+  border: 1px solid #1fa0eb;
+  box-shadow: 0 0 2px #1fa0eb;
+}
 
 /* Docgen styles */
 /* Links */
diff --git a/nimdoc/test_out_index_dot_html/expected/index.html b/nimdoc/test_out_index_dot_html/expected/index.html
index 1dbcdd51c0..c9d582dc3b 100644
--- a/nimdoc/test_out_index_dot_html/expected/index.html
+++ b/nimdoc/test_out_index_dot_html/expected/index.html
@@ -99,6 +99,23 @@ input#searchInput {
   width: 80%;
 }
 
+/*
+ * Some custom formatting for input forms.
+ * This also fixes input form colors on Firefox with a dark system theme on Linux.
+ */
+input {
+  -moz-appearance: none;
+  color: #333;
+  background-color: #f8f8f8;
+  border: 1px solid #aaa;
+  font-family: "Lato", "Helvetica Neue", "HelveticaNeue", Helvetica, Arial, sans-serif;
+  font-size: 0.9em;
+  padding: 6px;
+}
+input:focus {
+  border: 1px solid #1fa0eb;
+  box-shadow: 0 0 2px #1fa0eb;
+}
 
 /* Docgen styles */
 /* Links */
diff --git a/nimdoc/test_out_index_dot_html/expected/theindex.html b/nimdoc/test_out_index_dot_html/expected/theindex.html
index 9213f14590..9a04738c28 100644
--- a/nimdoc/test_out_index_dot_html/expected/theindex.html
+++ b/nimdoc/test_out_index_dot_html/expected/theindex.html
@@ -99,6 +99,23 @@ input#searchInput {
   width: 80%;
 }
 
+/*
+ * Some custom formatting for input forms.
+ * This also fixes input form colors on Firefox with a dark system theme on Linux.
+ */
+input {
+  -moz-appearance: none;
+  color: #333;
+  background-color: #f8f8f8;
+  border: 1px solid #aaa;
+  font-family: "Lato", "Helvetica Neue", "HelveticaNeue", Helvetica, Arial, sans-serif;
+  font-size: 0.9em;
+  padding: 6px;
+}
+input:focus {
+  border: 1px solid #1fa0eb;
+  box-shadow: 0 0 2px #1fa0eb;
+}
 
 /* Docgen styles */
 /* Links */
diff --git a/nimdoc/testproject/expected/subdir/subdir_b/utils.html b/nimdoc/testproject/expected/subdir/subdir_b/utils.html
index 6f7a0c6e42..478854a1e9 100644
--- a/nimdoc/testproject/expected/subdir/subdir_b/utils.html
+++ b/nimdoc/testproject/expected/subdir/subdir_b/utils.html
@@ -99,6 +99,23 @@ input#searchInput {
   width: 80%;
 }
 
+/*
+ * Some custom formatting for input forms.
+ * This also fixes input form colors on Firefox with a dark system theme on Linux.
+ */
+input {
+  -moz-appearance: none;
+  color: #333;
+  background-color: #f8f8f8;
+  border: 1px solid #aaa;
+  font-family: "Lato", "Helvetica Neue", "HelveticaNeue", Helvetica, Arial, sans-serif;
+  font-size: 0.9em;
+  padding: 6px;
+}
+input:focus {
+  border: 1px solid #1fa0eb;
+  box-shadow: 0 0 2px #1fa0eb;
+}
 
 /* Docgen styles */
 /* Links */
diff --git a/nimdoc/testproject/expected/testproject.html b/nimdoc/testproject/expected/testproject.html
index 1b2458a9be..273defbbfb 100644
--- a/nimdoc/testproject/expected/testproject.html
+++ b/nimdoc/testproject/expected/testproject.html
@@ -99,6 +99,23 @@ input#searchInput {
   width: 80%;
 }
 
+/*
+ * Some custom formatting for input forms.
+ * This also fixes input form colors on Firefox with a dark system theme on Linux.
+ */
+input {
+  -moz-appearance: none;
+  color: #333;
+  background-color: #f8f8f8;
+  border: 1px solid #aaa;
+  font-family: "Lato", "Helvetica Neue", "HelveticaNeue", Helvetica, Arial, sans-serif;
+  font-size: 0.9em;
+  padding: 6px;
+}
+input:focus {
+  border: 1px solid #1fa0eb;
+  box-shadow: 0 0 2px #1fa0eb;
+}
 
 /* Docgen styles */
 /* Links */
diff --git a/nimdoc/testproject/expected/theindex.html b/nimdoc/testproject/expected/theindex.html
index 58cab3ef31..f97ea54b92 100644
--- a/nimdoc/testproject/expected/theindex.html
+++ b/nimdoc/testproject/expected/theindex.html
@@ -99,6 +99,23 @@ input#searchInput {
   width: 80%;
 }
 
+/*
+ * Some custom formatting for input forms.
+ * This also fixes input form colors on Firefox with a dark system theme on Linux.
+ */
+input {
+  -moz-appearance: none;
+  color: #333;
+  background-color: #f8f8f8;
+  border: 1px solid #aaa;
+  font-family: "Lato", "Helvetica Neue", "HelveticaNeue", Helvetica, Arial, sans-serif;
+  font-size: 0.9em;
+  padding: 6px;
+}
+input:focus {
+  border: 1px solid #1fa0eb;
+  box-shadow: 0 0 2px #1fa0eb;
+}
 
 /* Docgen styles */
 /* Links */