diff --git a/pkg/yqlib/lib.go b/pkg/yqlib/lib.go
index 433a5572..1503572b 100644
--- a/pkg/yqlib/lib.go
+++ b/pkg/yqlib/lib.go
@@ -8,14 +8,24 @@ import (
 	"math"
 	"strconv"
 	"strings"
+	"sync"
 )
 
 var ExpressionParser ExpressionParserInterface
 
+var expressionParserOnce sync.Once
+
+// InitExpressionParser initialises the package level ExpressionParser, and is
+// safe to call concurrently. The evaluators call it on every Evaluate, so
+// without the guard two goroutines could construct a parser at the same time,
+// and newParticipleLexer populates the shared participleYqRules entries as it
+// goes, which a third goroutine could be reading through getYqDefinition.
 func InitExpressionParser() {
-	if ExpressionParser == nil {
-		ExpressionParser = newExpressionParser()
-	}
+	expressionParserOnce.Do(func() {
+		if ExpressionParser == nil {
+			ExpressionParser = newExpressionParser()
+		}
+	})
 }
 
 var log = newLogger()
diff --git a/pkg/yqlib/lib_test.go b/pkg/yqlib/lib_test.go
index f35ebb4f..4e031dfd 100644
--- a/pkg/yqlib/lib_test.go
+++ b/pkg/yqlib/lib_test.go
@@ -3,6 +3,7 @@ package yqlib
 import (
 	"fmt"
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/mikefarah/yq/v4/test"
@@ -555,3 +556,39 @@ func TestProcessEscapeCharacters(t *testing.T) {
 		test.AssertResultComplexWithContext(t, tt.expected, actual, fmt.Sprintf("Input: %q", tt.input))
 	}
 }
+
+// TestInitExpressionParserConcurrent covers the data race described in #2788.
+// The evaluators call InitExpressionParser on every Evaluate, so before it was
+// guarded two goroutines could build a parser at the same time while a third
+// read the shared participleYqRules entries that newParticipleLexer fills in.
+//
+// To reproduce the original race the process must not have initialised the
+// parser yet, so run this test on its own with the detector enabled:
+//
+//	go test -race -run TestInitExpressionParserConcurrent ./pkg/yqlib/
+func TestInitExpressionParserConcurrent(t *testing.T) {
+	const goroutines = 32
+
+	var wg sync.WaitGroup
+	errs := make(chan error, goroutines)
+
+	for range goroutines {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			InitExpressionParser()
+			if _, err := ExpressionParser.ParseExpression(".a.b"); err != nil {
+				errs <- err
+			}
+		}()
+	}
+	wg.Wait()
+	close(errs)
+
+	for err := range errs {
+		t.Fatalf("concurrent ParseExpression failed: %v", err)
+	}
+	if ExpressionParser == nil {
+		t.Fatal("ExpressionParser should be initialised after concurrent InitExpressionParser calls")
+	}
+}