diff --git a/api/Cargo.toml b/api/Cargo.toml
index ad1c3c9..9a198cc 100644
--- a/api/Cargo.toml
+++ b/api/Cargo.toml
@@ -20,4 +20,4 @@ generalized = []
 sophia = ["sophia_api"]
 
 [dependencies]
-sophia_api = { version = "0.6", optional = true }
+sophia_api = { version = ">=0.6,<=0.7", optional = true }
diff --git a/turtle/Cargo.toml b/turtle/Cargo.toml
index 4431489..978737f 100644
--- a/turtle/Cargo.toml
+++ b/turtle/Cargo.toml
@@ -23,8 +23,8 @@ sophia = ["rio_api/sophia", "sophia_api"]
 oxilangtag = "0.1"
 oxiri = "0.1"
 rio_api = { version = "0.6", path="../api" }
-sophia_api = { version = "0.6", optional = true }
+sophia_api = { version = ">=0.6,<=0.7", optional = true }
 
 [dev-dependencies]
-sophia_api = { version = "0.6", features = ["test_macro"] }
+sophia_api = { version = ">=0.6,<=0.7", features = ["test_macro"] }
 
diff --git a/xml/Cargo.toml b/xml/Cargo.toml
index ecdbae2..0eefb5b 100644
--- a/xml/Cargo.toml
+++ b/xml/Cargo.toml
@@ -23,7 +23,7 @@ oxilangtag = "0.1"
 oxiri = "0.1"
 rio_api = { version = "0.6", path="../api" }
 quick-xml = "0.22"
-sophia_api = { version = "0.6", optional = true }
+sophia_api = { version = ">=0.6,<=0.7", optional = true }
 
 [dev-dependencies]
-sophia_api = { version = "0.6", features = ["test_macro"] }
+sophia_api = { version = ">=0.6,<=0.7", features = ["test_macro"] }