diff --git a/examples/ex19.jl b/examples/ex19.jl
index 11539c5b..7539eb8c 100644
--- a/examples/ex19.jl
+++ b/examples/ex19.jl
@@ -258,7 +258,13 @@ end
 opts     = isinteractive() ? NamedTuple() : PETSc.parse_options(filter(a -> a != "-log_view", ARGS))
 log_view = "-log_view" in ARGS
 
-petsclib = PETSc.getlib(; PetscScalar = Float64, PetscInt = Int32)
+petsclib = try
+    PETSc.getlib(; PetscScalar = Float64, PetscInt = Int32)
+catch
+    # Fall back to any available Float64 library (e.g. when only the
+    # Int64 variants are built, or with a set_library! custom library)
+    first(filter(l -> PETSc.scalartype(l) == Float64, collect(PETSc.petsclibs)))
+end
 PETSc.initialize(petsclib; log_view)
 
 _T        = Float64
diff --git a/src/LibPETSc_startup.jl b/src/LibPETSc_startup.jl
index a6078304..42dc6038 100644
--- a/src/LibPETSc_startup.jl
+++ b/src/LibPETSc_startup.jl
@@ -16,18 +16,29 @@ using Preferences
 
 # @load_preference is evaluated at compile time; changing a preference via
 # set_library!() triggers automatic recompilation (standard Preferences.jl behaviour).
+#
+# Only ONE PetscInt width is registered per process (default Int64,
+# switchable with the "PetscInt" preference / `set_petscint!`).  The Int64
+# and Int32 libpetsc variants link external packages that export identical
+# symbols with different integer ABIs (hypre, SuperLU_DIST), so loading
+# both widths into one flat ELF namespace cross-binds those symbols.
 const libs = @static if @load_preference("library_path", nothing) === nothing
     using PETSc_jll
-    (
-        ((PETSc_jll.libpetsc_Float64_Real_Int64,), Float64, Int64),
-        ((PETSc_jll.libpetsc_Float32_Real_Int64,), Float32, Int64),
-        ((PETSc_jll.libpetsc_Float64_Complex_Int64,), Complex{Float64}, Int64),
-        ((PETSc_jll.libpetsc_Float32_Complex_Int64,), Complex{Float32}, Int64),
-        ((PETSc_jll.libpetsc_Float64_Real_Int32,), Float64, Int32),
-        ((PETSc_jll.libpetsc_Float32_Real_Int32,), Float32, Int32),
-        ((PETSc_jll.libpetsc_Float64_Complex_Int32,), Complex{Float64}, Int32),
-        ((PETSc_jll.libpetsc_Float32_Complex_Int32,), Complex{Float32}, Int32),
-    )
+    @static if @load_preference("PetscInt", "Int64") == "Int32"
+        (
+            ((PETSc_jll.libpetsc_Float64_Real_Int32,), Float64, Int32),
+            ((PETSc_jll.libpetsc_Float32_Real_Int32,), Float32, Int32),
+            ((PETSc_jll.libpetsc_Float64_Complex_Int32,), Complex{Float64}, Int32),
+            ((PETSc_jll.libpetsc_Float32_Complex_Int32,), Complex{Float32}, Int32),
+        )
+    else
+        (
+            ((PETSc_jll.libpetsc_Float64_Real_Int64,), Float64, Int64),
+            ((PETSc_jll.libpetsc_Float32_Real_Int64,), Float32, Int64),
+            ((PETSc_jll.libpetsc_Float64_Complex_Int64,), Complex{Float64}, Int64),
+            ((PETSc_jll.libpetsc_Float32_Complex_Int64,), Complex{Float32}, Int64),
+        )
+    end
 else
     let _path   = @load_preference("library_path"),
         _scalar = @load_preference("PetscScalar", "Float64"),
diff --git a/src/PETSc.jl b/src/PETSc.jl
index 49d109f3..4c051aa2 100644
--- a/src/PETSc.jl
+++ b/src/PETSc.jl
@@ -23,7 +23,7 @@ using .LibPETSc
 export LibPETSc
 export audit_petsc_file
 export set_petsclib
-export set_library!, unset_library!, library_info
+export set_library!, unset_library!, set_petscint!, library_info
 export AbstractPETScMemBackend, HostBackend
 export determine_memtype
 export get_petsc_arrays, restore_petsc_arrays
diff --git a/src/init.jl b/src/init.jl
index b68e0bf2..e24f4763 100644
--- a/src/init.jl
+++ b/src/init.jl
@@ -337,6 +337,25 @@ function unset_library!()
     @info "PETSc library preference removed — restart Julia to revert to PETSc_jll."
 end
 
+"""
+    set_petscint!(::Type{T}) where {T<:Union{Int32,Int64}}
+
+Persistently select which `PetscInt` width of the `PETSc_jll` libraries is
+loaded (default: `Int64`).  Only one width is registered per process: the
+Int64 and Int32 library variants link external packages (hypre,
+SuperLU_DIST) that export identical symbols with different integer ABIs,
+so mixing both widths in one process is unsafe on platforms with a flat
+dynamic-linker namespace.
+
+Takes effect on the next Julia session (standard Preferences.jl
+recompilation).  Has no effect when a custom library is configured via
+[`set_library!`](@ref).
+"""
+function set_petscint!(::Type{T}) where {T<:Union{Int32,Int64}}
+    @set_preferences!("PetscInt" => string(T))
+    @info "PETSc_jll PetscInt width set — restart Julia to use it." PetscInt = T
+end
+
 
 """
     check_petsc_wrappers_version(petsclib=nothing)
diff --git a/test/dmda.jl b/test/dmda.jl
index c39a9587..e2731057 100644
--- a/test/dmda.jl
+++ b/test/dmda.jl
@@ -345,7 +345,7 @@ end
     mpirank = MPI.Comm_rank(comm)
     mpisize = MPI.Comm_size(comm)
     # Just check a couple libraries
-    for petsclib in PETSc.petsclibs[1:2]
+    for petsclib in PETSc.petsclibs[1:min(2, length(PETSc.petsclibs))]
         #petsclib = PETSc.petsclibs[1]
         PETSc.initialize(petsclib)
         PetscScalar = petsclib.PetscScalar
diff --git a/test/init.jl b/test/init.jl
index f331f6d3..a88ff648 100644
--- a/test/init.jl
+++ b/test/init.jl
@@ -185,12 +185,15 @@ using PETSc
         PETSc.finalize(custom_lib)
         @test !PETSc.initialized(custom_lib)
         
-        # Test with different scalar/int types
-        lib_path_f32 = PETSc.petsclibs[2].petsc_library  # Float32 library
-        custom_lib_f32 = PETSc.set_petsclib(lib_path_f32; PetscScalar=Float32, PetscInt=Int64)
-        @test custom_lib_f32 isa PETSc.LibPETSc.PetscLibType{Float32, Int64, String}
-        @test PETSc.scalartype(custom_lib_f32) == Float32
-        @test PETSc.inttype(custom_lib_f32) == Int64
+        # Test with different scalar/int types (only when more than one
+        # library is configured; with set_library! there is just one)
+        if length(PETSc.petsclibs) >= 2
+            lib_path_f32 = PETSc.petsclibs[2].petsc_library  # Float32 library
+            custom_lib_f32 = PETSc.set_petsclib(lib_path_f32; PetscScalar=Float32, PetscInt=Int64)
+            @test custom_lib_f32 isa PETSc.LibPETSc.PetscLibType{Float32, Int64, String}
+            @test PETSc.scalartype(custom_lib_f32) == Float32
+            @test PETSc.inttype(custom_lib_f32) == Int64
+        end
     end
 end
 
diff --git a/test/test_dmstag.jl b/test/test_dmstag.jl
index 2b14cabc..a290803f 100644
--- a/test/test_dmstag.jl
+++ b/test/test_dmstag.jl
@@ -11,7 +11,7 @@ end
     comm = Sys.iswindows() ? LibPETSc.PETSC_COMM_SELF : MPI.COMM_WORLD
     mpirank = MPI.Comm_rank(comm)
     mpisize = MPI.Comm_size(comm)
-    for petsclib in PETSc.petsclibs[1:4]
+    for petsclib in PETSc.petsclibs[1:min(4, length(PETSc.petsclibs))]
         #petsclib = PETSc.petsclibs[1]
         PETSc.initialize(petsclib)
         PetscScalar = PETSc.scalartype(petsclib)
@@ -471,7 +471,7 @@ end
     comm = Sys.iswindows() ? LibPETSc.PETSC_COMM_SELF : MPI.COMM_WORLD
     mpirank = MPI.Comm_rank(comm)
     mpisize = MPI.Comm_size(comm)
-    for petsclib in PETSc.petsclibs[1:4]
+    for petsclib in PETSc.petsclibs[1:min(4, length(PETSc.petsclibs))]
         #@show petsclib
         #petsclib = PETSc.petsclibs[1]
     
@@ -606,7 +606,7 @@ end
     comm = Sys.iswindows() ? LibPETSc.PETSC_COMM_SELF : MPI.COMM_WORLD
     mpirank = MPI.Comm_rank(comm)
     mpisize = MPI.Comm_size(comm)
-    for petsclib in PETSc.petsclibs[1:2]
+    for petsclib in PETSc.petsclibs[1:min(2, length(PETSc.petsclibs))]
         #petsclib = PETSc.petsclibs[1]
         PETSc.initialize(petsclib, log_view=false)
         PetscScalar = PETSc.scalartype(petsclib)
@@ -736,7 +736,7 @@ end
 
 @testset "DMStagVecGetArray/RestoreArray" begin
     comm = Sys.iswindows() ? LibPETSc.PETSC_COMM_SELF : MPI.COMM_WORLD
-    for petsclib in PETSc.petsclibs[1:4]
+    for petsclib in PETSc.petsclibs[1:min(4, length(PETSc.petsclibs))]
         PETSc.initialize(petsclib)
         PetscScalar = PETSc.scalartype(petsclib)
         PetscInt    = PETSc.inttype(petsclib)
diff --git a/test/vec.jl b/test/vec.jl
index a5a9add2..de8e66f2 100644
--- a/test/vec.jl
+++ b/test/vec.jl
@@ -89,7 +89,7 @@ end
 
 @testset "VecCreateSeqWithArray" begin
     N = 10
-    for petsclib in PETSc.petsclibs[1:2]
+    for petsclib in PETSc.petsclibs[1:min(2, length(PETSc.petsclibs))]
         #petsclib = PETSc.petsclibs[5]
         PETSc.initialize(petsclib)
         PetscScalar = petsclib.PetscScalar