diff --git a/deltachat-ffi/src/lib.rs b/deltachat-ffi/src/lib.rs
index 7a5e77ba5..87fb7282f 100644
--- a/deltachat-ffi/src/lib.rs
+++ b/deltachat-ffi/src/lib.rs
@@ -56,9 +56,16 @@ pub unsafe extern "C" fn dc_open(
     blobdir: *mut libc::c_char,
 ) -> libc::c_int {
     assert!(!context.is_null());
+    assert!(!dbfile.is_null());
     let context = &mut *context;
 
-    context::dc_open(context, dbfile, blobdir)
+    let dbfile_str = dc_tools::as_str(dbfile);
+    let blobdir_str = if blobdir.is_null() {
+        None
+    } else {
+        Some(dc_tools::as_str(blobdir))
+    };
+    context::dc_open(context, dbfile_str, blobdir_str) as libc::c_int
 }
 
 #[no_mangle]
diff --git a/examples/repl/cmdline.rs b/examples/repl/cmdline.rs
index 09c0225a6..8f6e2d2e6 100644
--- a/examples/repl/cmdline.rs
+++ b/examples/repl/cmdline.rs
@@ -503,10 +503,7 @@ pub unsafe fn dc_cmdline(context: &Context, line: &str) -> Result<(), failure::E
         "open" => {
             ensure!(!arg1.is_empty(), "Argument <file> missing");
             dc_close(context);
-            ensure!(
-                0 != dc_open(context, arg1_c, 0 as *const libc::c_char),
-                "Open failed"
-            );
+            ensure!(dc_open(context, arg1, None), "Open failed");
         }
         "close" => {
             dc_close(context);
diff --git a/examples/repl/main.rs b/examples/repl/main.rs
index 7cc700af8..214527467 100644
--- a/examples/repl/main.rs
+++ b/examples/repl/main.rs
@@ -399,12 +399,7 @@ fn main_0(args: Vec<String>) -> Result<(), failure::Error> {
     unsafe { dc_cmdline_skip_auth() };
 
     if args.len() == 2 {
-        if 0 == unsafe {
-            let a = to_cstring(&args[1]);
-            let res = dc_open(&mut context, a, 0 as *const _);
-            free(a as *mut _);
-            res
-        } {
+        if unsafe { !dc_open(&mut context, &args[1], None) } {
             println!("Error: Cannot open {}.", args[0],);
         }
     } else if args.len() != 1 {
diff --git a/examples/simple.rs b/examples/simple.rs
index 4a9b0c1fc..2aa824acb 100644
--- a/examples/simple.rs
+++ b/examples/simple.rs
@@ -76,11 +76,11 @@ fn main() {
         });
 
         let dir = tempdir().unwrap();
-        let dbfile = CString::new(dir.path().join("db.sqlite").to_str().unwrap()).unwrap();
+        let dbfile = dir.path().join("db.sqlite");
 
         println!("opening database {:?}", dbfile);
 
-        assert_eq!(dc_open(&ctx, dbfile.as_ptr(), std::ptr::null()), 1);
+        assert!(dc_open(&ctx, dbfile.to_str().unwrap(), None));
 
         println!("configuring");
         let args = std::env::args().collect::<Vec<String>>();
diff --git a/src/context.rs b/src/context.rs
index 1bbc8a986..6f9a1b2f1 100644
--- a/src/context.rs
+++ b/src/context.rs
@@ -315,32 +315,26 @@ pub unsafe fn dc_get_userdata(context: &mut Context) -> *mut libc::c_void {
     context.userdata as *mut _
 }
 
-pub unsafe fn dc_open(
-    context: &Context,
-    dbfile: *const libc::c_char,
-    blobdir: *const libc::c_char,
-) -> libc::c_int {
-    let mut success = 0;
+pub unsafe fn dc_open(context: &Context, dbfile: &str, blobdir: Option<&str>) -> bool {
+    let mut success = false;
     if 0 != dc_is_open(context) {
-        return 0;
+        return false;
     }
-    if !dbfile.is_null() {
-        *context.dbfile.write().unwrap() = dc_strdup(dbfile);
-        if !blobdir.is_null() && 0 != *blobdir.offset(0isize) as libc::c_int {
-            let dir = dc_strdup(blobdir);
-            dc_ensure_no_slash(dir);
-            *context.blobdir.write().unwrap() = dir;
-        } else {
-            let dir = dc_mprintf(b"%s-blobs\x00" as *const u8 as *const libc::c_char, dbfile);
-            dc_create_folder(context, dir);
-            *context.blobdir.write().unwrap() = dir;
-        }
-        // Create/open sqlite database, this may already use the blobdir
-        if context.sql.open(context, as_path(dbfile), 0) {
-            success = 1i32
-        }
+    *context.dbfile.write().unwrap() = to_cstring(dbfile);
+    if blobdir.is_some() && blobdir.unwrap().len() > 0 {
+        let dir = to_cstring(dc_ensure_no_slash_safe(blobdir.unwrap()));
+        *context.blobdir.write().unwrap() = dir;
+    } else {
+        let dir = to_cstring(dbfile.to_string() + "-blobs");
+        dc_create_folder(context, dir);
+        *context.blobdir.write().unwrap() = dir;
     }
-    if 0 == success {
+    // Create/open sqlite database, this may already use the blobdir
+    let dbfile_path = std::path::Path::new(dbfile);
+    if context.sql.open(context, dbfile_path, 0) {
+        success = true
+    }
+    if !success {
         dc_close(context);
     }
     success
diff --git a/src/peerstate.rs b/src/peerstate.rs
index 876a300b1..7d0f2f648 100644
--- a/src/peerstate.rs
+++ b/src/peerstate.rs
@@ -462,12 +462,9 @@ mod tests {
     use super::*;
     use pretty_assertions::assert_eq;
 
-    use std::ffi::CStr;
     use tempfile::{tempdir, TempDir};
 
     use crate::context::*;
-    use crate::dc_tools::to_cstring;
-    use crate::x::free;
 
     #[test]
     fn test_peerstate_save_to_db() {
@@ -522,16 +519,13 @@ mod tests {
     unsafe fn create_test_context() -> TestContext {
         let mut ctx = dc_context_new(Some(cb), std::ptr::null_mut(), std::ptr::null_mut());
         let dir = tempdir().unwrap();
-        let dbfile = to_cstring(dir.path().join("db.sqlite").to_str().unwrap());
-        assert_eq!(
-            dc_open(&mut ctx, dbfile, std::ptr::null()),
-            1,
+        let dbfile = dir.path().join("db.sqlite");
+        assert!(
+            dc_open(&mut ctx, dbfile.to_str().unwrap(), None),
             "Failed to open {}",
-            CStr::from_ptr(dbfile as *const _).to_str().unwrap()
+            dbfile.to_str().unwrap()
         );
 
-        free(dbfile as *mut _);
-
         TestContext { ctx: ctx, dir: dir }
     }
 }
diff --git a/src/test_utils.rs b/src/test_utils.rs
index 1109bd4ec..f78aa14e6 100644
--- a/src/test_utils.rs
+++ b/src/test_utils.rs
@@ -7,8 +7,6 @@ use tempfile::{tempdir, TempDir};
 use crate::context::{dc_context_new, dc_open, Context};
 use crate::types::dc_callback_t;
 
-use crate::dc_tools::OsStrExt;
-
 /// A Context and temporary directory.
 ///
 /// The temporary directory can be used to store the SQLite database,
@@ -29,10 +27,8 @@ pub fn test_context(cb: Option<dc_callback_t>) -> TestContext {
         let mut ctx = dc_context_new(cb, std::ptr::null_mut(), std::ptr::null_mut());
         let dir = tempdir().unwrap();
         let dbfile = dir.path().join("db.sqlite");
-        let dbfile_c = dbfile.to_c_string().unwrap();
-        assert_eq!(
-            dc_open(&mut ctx, dbfile_c.as_ptr(), std::ptr::null()),
-            1,
+        assert!(
+            dc_open(&mut ctx, dbfile.to_str().unwrap(), None),
             "Failed to open {}",
             dbfile.display(),
         );
diff --git a/tests/stress.rs b/tests/stress.rs
index d5518b9e2..912879374 100644
--- a/tests/stress.rs
+++ b/tests/stress.rs
@@ -817,14 +817,12 @@ struct TestContext {
 unsafe fn create_test_context() -> TestContext {
     let mut ctx = dc_context_new(Some(cb), std::ptr::null_mut(), std::ptr::null_mut());
     let dir = tempdir().unwrap();
-    let dbfile = to_cstring(dir.path().join("db.sqlite").to_str().unwrap());
-    assert_eq!(
-        dc_open(&mut ctx, dbfile, std::ptr::null()),
-        1,
+    let dbfile = dir.path().join("db.sqlite");
+    assert!(
+        dc_open(&mut ctx, dbfile.to_str().unwrap(), None),
         "Failed to open {}",
-        as_str(dbfile as *const libc::c_char)
+        dbfile.to_str().unwrap()
     );
-    free(dbfile as *mut _);
     TestContext { ctx: ctx, dir: dir }
 }
 
@@ -1006,9 +1004,7 @@ fn test_wrong_db() {
         let dbfile = dir.path().join("db.sqlite");
         std::fs::write(&dbfile, b"123").unwrap();
 
-        let dbfile_c = to_cstring(dbfile.to_str().unwrap());
-        let res = dc_open(&mut ctx, dbfile_c, std::ptr::null());
-        free(dbfile_c as *mut _);
-        assert_eq!(res, 0);
+        let res = dc_open(&mut ctx, dbfile.to_str().unwrap(), None);
+        assert!(!res);
     }
 }