diff --git a/toolchain/diagnostics/diagnostic_kind.def b/toolchain/diagnostics/diagnostic_kind.def
index 8a6f33a69eef..4eaefcb8eb37 100644
--- a/toolchain/diagnostics/diagnostic_kind.def
+++ b/toolchain/diagnostics/diagnostic_kind.def
@@ -64,7 +64,7 @@ CARBON_DIAGNOSTIC_KIND(ExpectedArraySemi)
 CARBON_DIAGNOSTIC_KIND(ExpectedCloseSymbol)
 CARBON_DIAGNOSTIC_KIND(ExpectedCodeBlock)
 CARBON_DIAGNOSTIC_KIND(ExpectedExpr)
-CARBON_DIAGNOSTIC_KIND(ExpectedIdentifierAfterDotOrArrow)
+CARBON_DIAGNOSTIC_KIND(ExpectedIdentifierAfterPeriodOrArrow)
 CARBON_DIAGNOSTIC_KIND(ExpectedBindingPattern)
 CARBON_DIAGNOSTIC_KIND(ExpectedParenAfter)
 CARBON_DIAGNOSTIC_KIND(ExpectedExprSemi)
diff --git a/toolchain/parse/handle_period.cpp b/toolchain/parse/handle_period.cpp
index 7675a8b0e720..d620c9437a08 100644
--- a/toolchain/parse/handle_period.cpp
+++ b/toolchain/parse/handle_period.cpp
@@ -35,10 +35,10 @@ static auto HandlePeriodOrArrow(Context& context, NodeKind node_kind,
     context.PushState(State::OnlyParenExpr);
     return;
   } else {
-    CARBON_DIAGNOSTIC(ExpectedIdentifierAfterDotOrArrow, Error,
+    CARBON_DIAGNOSTIC(ExpectedIdentifierAfterPeriodOrArrow, Error,
                       "Expected identifier after `{0}`.", llvm::StringLiteral);
     context.emitter().Emit(
-        *context.position(), ExpectedIdentifierAfterDotOrArrow,
+        *context.position(), ExpectedIdentifierAfterPeriodOrArrow,
         is_arrow ? llvm::StringLiteral("->") : llvm::StringLiteral("."));
     // If we see a keyword, assume it was intended to be a name.
     // TODO: Should keywords be valid here?
diff --git a/toolchain/parse/testdata/struct/fail_dot_only.carbon b/toolchain/parse/testdata/struct/fail_period_only.carbon
similarity index 84%
rename from toolchain/parse/testdata/struct/fail_dot_only.carbon
rename to toolchain/parse/testdata/struct/fail_period_only.carbon
index 2876ae99cd15..7b491126689e 100644
--- a/toolchain/parse/testdata/struct/fail_dot_only.carbon
+++ b/toolchain/parse/testdata/struct/fail_period_only.carbon
@@ -4,16 +4,16 @@
 //
 // AUTOUPDATE
 // TIP: To test this file alone, run:
-// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_dot_only.carbon
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_period_only.carbon
 // TIP: To dump output, run:
-// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_dot_only.carbon
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_period_only.carbon
 
-// CHECK:STDERR: fail_dot_only.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
+// CHECK:STDERR: fail_period_only.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
 // CHECK:STDERR: var x: {.} = {};
 // CHECK:STDERR:          ^
 var x: {.} = {};
 
-// CHECK:STDOUT: - filename: fail_dot_only.carbon
+// CHECK:STDOUT: - filename: fail_period_only.carbon
 // CHECK:STDOUT:   parse_tree: [
 // CHECK:STDOUT:     {kind: 'FileStart', text: ''},
 // CHECK:STDOUT:       {kind: 'VariableIntroducer', text: 'var'},
diff --git a/toolchain/parse/testdata/struct/fail_dot_paren.carbon b/toolchain/parse/testdata/struct/fail_period_paren.carbon
similarity index 82%
rename from toolchain/parse/testdata/struct/fail_dot_paren.carbon
rename to toolchain/parse/testdata/struct/fail_period_paren.carbon
index 22b6c4ef9d50..0d2d121cc9f1 100644
--- a/toolchain/parse/testdata/struct/fail_dot_paren.carbon
+++ b/toolchain/parse/testdata/struct/fail_period_paren.carbon
@@ -4,16 +4,16 @@
 //
 // AUTOUPDATE
 // TIP: To test this file alone, run:
-// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_dot_paren.carbon
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_period_paren.carbon
 // TIP: To dump output, run:
-// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_dot_paren.carbon
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_period_paren.carbon
 
-// CHECK:STDERR: fail_dot_paren.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
+// CHECK:STDERR: fail_period_paren.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
 // CHECK:STDERR: var x: {.(a) = 1};
 // CHECK:STDERR:          ^
 var x: {.(a) = 1};
 
-// CHECK:STDOUT: - filename: fail_dot_paren.carbon
+// CHECK:STDOUT: - filename: fail_period_paren.carbon
 // CHECK:STDOUT:   parse_tree: [
 // CHECK:STDOUT:     {kind: 'FileStart', text: ''},
 // CHECK:STDOUT:       {kind: 'VariableIntroducer', text: 'var'},
diff --git a/toolchain/parse/testdata/struct/fail_dot_string_colon.carbon b/toolchain/parse/testdata/struct/fail_period_string_colon.carbon
similarity index 86%
rename from toolchain/parse/testdata/struct/fail_dot_string_colon.carbon
rename to toolchain/parse/testdata/struct/fail_period_string_colon.carbon
index ffcaa1e2f2ba..b0be9b6a1887 100644
--- a/toolchain/parse/testdata/struct/fail_dot_string_colon.carbon
+++ b/toolchain/parse/testdata/struct/fail_period_string_colon.carbon
@@ -4,16 +4,16 @@
 //
 // AUTOUPDATE
 // TIP: To test this file alone, run:
-// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_dot_string_colon.carbon
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_period_string_colon.carbon
 // TIP: To dump output, run:
-// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_dot_string_colon.carbon
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_period_string_colon.carbon
 
-// CHECK:STDERR: fail_dot_string_colon.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
+// CHECK:STDERR: fail_period_string_colon.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
 // CHECK:STDERR: var x: {."hello": i32, .y: i32} = {};
 // CHECK:STDERR:          ^~~~~~~
 var x: {."hello": i32, .y: i32} = {};
 
-// CHECK:STDOUT: - filename: fail_dot_string_colon.carbon
+// CHECK:STDOUT: - filename: fail_period_string_colon.carbon
 // CHECK:STDOUT:   parse_tree: [
 // CHECK:STDOUT:     {kind: 'FileStart', text: ''},
 // CHECK:STDOUT:       {kind: 'VariableIntroducer', text: 'var'},
diff --git a/toolchain/parse/testdata/struct/fail_dot_string_equals.carbon b/toolchain/parse/testdata/struct/fail_period_string_equals.carbon
similarity index 86%
rename from toolchain/parse/testdata/struct/fail_dot_string_equals.carbon
rename to toolchain/parse/testdata/struct/fail_period_string_equals.carbon
index beb677cfceaf..41484b8c8dcd 100644
--- a/toolchain/parse/testdata/struct/fail_dot_string_equals.carbon
+++ b/toolchain/parse/testdata/struct/fail_period_string_equals.carbon
@@ -4,16 +4,16 @@
 //
 // AUTOUPDATE
 // TIP: To test this file alone, run:
-// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_dot_string_equals.carbon
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/parse/testdata/struct/fail_period_string_equals.carbon
 // TIP: To dump output, run:
-// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_dot_string_equals.carbon
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/struct/fail_period_string_equals.carbon
 
-// CHECK:STDERR: fail_dot_string_equals.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
+// CHECK:STDERR: fail_period_string_equals.carbon:[[@LINE+3]]:10: ERROR: Expected identifier after `.`.
 // CHECK:STDERR: var x: {."hello" = 0, .y = 4} = {};
 // CHECK:STDERR:          ^~~~~~~
 var x: {."hello" = 0, .y = 4} = {};
 
-// CHECK:STDOUT: - filename: fail_dot_string_equals.carbon
+// CHECK:STDOUT: - filename: fail_period_string_equals.carbon
 // CHECK:STDOUT:   parse_tree: [
 // CHECK:STDOUT:     {kind: 'FileStart', text: ''},
 // CHECK:STDOUT:       {kind: 'VariableIntroducer', text: 'var'},