diff --git a/osv/json.go b/osv/json.go
index 8e19f9a..c634d98 100644
--- a/osv/json.go
+++ b/osv/json.go
@@ -55,8 +55,8 @@
 
 type AffectsRange struct {
 	Type       AffectsRangeType `json:"type"`
-	Introduced string           `json:"introduced"`
-	Fixed      string           `json:"fixed"`
+	Introduced string           `json:"introduced,omitempty"`
+	Fixed      string           `json:"fixed,omitempty"`
 }
 
 // addSemverPrefix adds a 'v' prefix to s if it isn't already prefixed
@@ -103,6 +103,12 @@
 			Fixed:      removeSemverPrefix(v.Fixed),
 		})
 	}
+	if len(a.Ranges) == 0 {
+		// If all versions are affected, as indicated by an empty versions slice,
+		// we need to include an empty TypeSemver AffectsRange in the JSON
+		// output.
+		a.Ranges = append(a.Ranges, AffectsRange{Type: TypeSemver})
+	}
 	return a
 }
 
diff --git a/osv/json_test.go b/osv/json_test.go
index ae0d69b..c306db0 100644
--- a/osv/json_test.go
+++ b/osv/json_test.go
@@ -143,6 +143,13 @@
 			want:    true,
 		},
 		{
+			// Affects containing an empty SEMVER range also indicates
+			// everything is affected
+			affects: Affects{Ranges: []AffectsRange{{Type: TypeSemver}}},
+			version: "v0.0.0",
+			want:    true,
+		},
+		{
 			// v1.0.0 < v2.0.0
 			affects: Affects{
 				Ranges: []AffectsRange{