diff --git a/amaranth/build/plat.py b/amaranth/build/plat.py
index fade608..7a0a13c 100644
--- a/amaranth/build/plat.py
+++ b/amaranth/build/plat.py
@@ -330,8 +330,15 @@ class TemplatedPlatform(Platform):
                     return f"_{ord(match.group(1)[0]):02x}_"
             return "".join(escape_one(m) for m in re.finditer(r"([^A-Za-z0-9_])|(.)", string))
 
-        def tcl_quote(string):
-            return '"' + re.sub(r"([$[\\])", r"\\\1", string) + '"'
+        def tcl_quote(string, quirk=None):
+            escaped = '"' + re.sub(r"([$[\\])", r"\\\1", string) + '"'
+            if quirk == "Diamond":
+                # Diamond seems to assign `clk\$2` as a name for the Verilog net `\clk$2 `, and
+                # `clk\\\$2` as a name for the Verilog net `\clk\$2 `.
+                return escaped.replace("\\", "\\\\")
+            else:
+                assert quirk is None
+                return escaped
 
         def verbose(arg):
             if get_override_flag("verbose"):
diff --git a/amaranth/vendor/_lattice.py b/amaranth/vendor/_lattice.py
index 9e001c9..834926f 100644
--- a/amaranth/vendor/_lattice.py
+++ b/amaranth/vendor/_lattice.py
@@ -686,9 +686,9 @@ class LatticePlatform(TemplatedPlatform):
             set_hierarchy_separator {/}
             {% for net_signal, port_signal, frequency in platform.iter_clock_constraints() -%}
                 {% if port_signal is not none -%}
-                    create_clock -name {{port_signal.name|tcl_quote}} -period {{1000000000/frequency}} [get_ports {{port_signal.name|tcl_quote}}]
+                    create_clock -name {{port_signal.name|tcl_quote("Diamond")}} -period {{1000000000/frequency}} [get_ports {{port_signal.name|tcl_quote("Diamond")}}]
                 {% else -%}
-                    create_clock -name {{net_signal.name|tcl_quote}} -period {{1000000000/frequency}} [get_nets {{net_signal|hierarchy("/")|tcl_quote}}]
+                    create_clock -name {{net_signal.name|tcl_quote("Diamond")}} -period {{1000000000/frequency}} [get_nets {{net_signal|hierarchy("/")|tcl_quote("Diamond")}}]
                 {% endif %}
             {% endfor %}
             {{get_override("add_constraints")|default("# (add_constraints placeholder)")}}